Cspc final

CSPC-COMPUTER SYSTEMS
PROGRAMMING IN ‘C’
ANKUR SRIVASTAVA
DEPARTMENT OF COMPUTER SCIENCE
31-Dec-16ANKUR SRIVASTAVA ASSISTANT PROFESSOR JETGI
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BASICS OF COMPUTER: INTRODUCTION TO DIGITAL COMPUTER, BASIC OPERATIONS
OF COMPUTER, FUNCTIONAL COMPONENTS OF COMPUTER, CLASSIFICATION OF
COMPUTERS.
INTRODUCTION TO OPERATING SYSTEM: [DOS, WINDOWS, LINUX AND ANDROID]
PURPOSE, FUNCTION, SERVICES AND TYPES.
NUMBER SYSTEM: BINARY, OCTAL AND HEXADECIMAL NUMBER SYSTEMS, THEIR
MUTUAL CONVERSIONS.
BINARY ARITHMETIC. BASICS OF PROGRAMMING: APPROACHES TO PROBLEM
SOLVING, CONCEPT OF ALGORITHM AND FLOWCHARTS.
TYPES OF COMPUTER LANGUAGES:- MACHINE LANGUAGE, ASSEMBLY LANGUAGE
AND HIGH LEVEL LANGUAGE, CONCEPT OF ASSEMBLER, COMPILER, LOADER AND
LINKER.
 UNIT-1 TOPICS
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STANDARD I/O IN “C”, FUNDAMENTAL DATA TYPES- CHARACTER TYPE, INTEGER,
SHORT, LONG, UNSIGNED, SINGLE AND DOUBLE FLOATING POINT.
STORAGE CLASSES- AUTOMATIC, REGISTER, STATIC AND EXTERNAL.
OPERATORS AND EXPRESSION USING NUMERIC AND RELATIONAL OPERATORS, MIXED
OPERANDS.
TYPE CONVERSION, LOGICAL OPERATORS, BIT OPERATIONS, ASSIGNMENT OPERATOR,
OPERATOR PRECEDENCE AND ASSOCIATIVELY.
FUNDAMENTALS OF C PROGRAMMING: STRUCTURE OF C PROGRAM, WRITING AND
EXECUTING THE FIRST C PROGRAM, COMPONENTS OF C LANGUAGE. STANDARD I/O
IN C.
 UNIT-2 TOPICS
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CONDITIONAL PROGRAM EXECUTION: APPLYING IF AND SWITCH
STATEMENTS, NESTING IF AND ELSE, USE OF BREAK AND DEFAULT WITH
SWITCH.
PROGRAM LOOPS AND ITERATIONS: USE OF WHILE, DO WHILE AND FOR
LOOPS, MULTIPLE LOOP VARIABLES, USE OF BREAK AND CONTINUE
STATEMENTS.
FUNCTIONS: INTRODUCTION, TYPES OF FUNCTIONS, FUNCTIONS WITH ARRAY,
PASSING VALUES TO FUNCTIONS, RECURSIVE FUNCTIONS.
 UNIT-3 TOPICS
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ARRAYS: ARRAY NOTATION AND REPRESENTATION, MANIPULATING ARRAY
ELEMENTS, USING MULTI-DIMENSIONAL ARRAYS.
STRUCTURE, UNION, ENUMERATED DATA TYPES.
 UNIT-4 TOPICS
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POINTERS: INTRODUCTION, DECLARATION, APPLICATIONS FILE HANDLING.
STANDARD C PREPROCESSORS, DEFINING AND CALLING MACROS.
CONDITIONAL COMPILATION, PASSING VALUES TO THE COMPILER.
 UNIT-5 TOPICS
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Some Basic Computer Understanding
1: What is a computer?
2: Different Types
3: Different Operating Systems
4: Different Brands
5: Basic Components
6: Hardware & Software
7: How a computer boots up
8: Different applications of a computer
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 Basics of Computer:
 Introduction to Digital Computer:- A Computer is an Electronic
device which takes Input and gives Output.
 Computers are machines that perform tasks or calculations
according to a set of instructions, or programs.
 It works through an interaction of Hardware & Software.
 Hardware items such as our monitor, keyboard, mouse, printer.
 Software such as System software and Application software.
 COMPUTER is a MACHINE that manipulates DATA according to a
list of INSTRUCTION. To accomplish a task using a computer,
need a combination of hardware, software .
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Printer Speakers UPS
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 Monitor
LCD CRT LED
CPU KEYBOARD MOUSE

Basic Operations of Computer:-
Program & Data
Results
Central Processing
Unit
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Input
Unit
Output
Unit
Storage
Unit
Control
Unit
Arithmetic
Logic Unit

 Basic Operations:
 Input Unit:- Information and Programs are entered into the COMPUTER
through Input Devices such as the KEYBOARD, DISKS, or through other Computers
via network connections or modems connected to the INTERNET. The Input
Device also retrieves information off Disks.
 Output Unit:- This unit takes care of receiving processed information from
processing unit & present it to the user in suitable form. A computer produces
results in binary form & output unit does Decoding to make it usable to the users.
 The devices that can output information from computer are known as output unit
devices. Monitors, Speakers, Projectors are soft output devices whereas printers,
plotters produces hard copy output.
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 Processing Unit:-
 The assignment of performing calculations and contrasts are known as
processing. The unit in Computer System that is accountable for
processing is ALU (Arithmetic and Logical Unit).
 ALU is the place where real execution of the instructions takes place
during the processing operations. All calculations & comparisons are
made in the ALU. The data and instructions deposited in the primary
storage are moved to it as when required. ALU may produce
Intermediate results and store it in the memory which are also transferred
back to the ALU for the final processing. After conclusion of processing
the final results are send to storage units from ALU.
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 Storage Unit:-
 Before actual processing start, data & directions entered to the computer
must be stored somewhere inside the computer. Similarly, results produced by
the computer are required to be stored before it is passed to the output unit.
The middle result created by the computer must also be kept for further
processing. Thus the status of storage Unit in a computer system is vital.
 Based on whether storage device is inside the main machine or not, it can be
internal internal or external storage. Similarly, looking at whether the storage
device works close with CPU or works as holdup media, they can be primary
storage or unimportant storage. Primary storage are also called primary
memory. Unimportant storage are known with other names such as backup
storage or secondary memory.
 For the storage purpose, a computer system may have different devices such
as registers, cache, RAM/ROM, flash, magnetic disks, optical disks and so on.
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 Control Unit:-
 It manages co-ordinates the entire system.
 CU doesn’t perform any actual processing on data yet it is known as a central
nervous system for the comforts of the computer.
 It controls all the processing & calculations of the ALU.
 It directs operation of the processor.
 It tells how to respond to a program's instructions.
 It directs the operation of the other units by providing timing and control signals.
 Most computer resources are managed by the CU.
 It directs the flow of data between the CPU and the other devices.
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 Functional Components of COMPUTER
 The five classic components of a Computer are as follows:-
 Processor(CPU)
 Main Memory
 Secondary Memory
 Input Devices
 Output Devices
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FIG. THE OPERATION OF A PROCESSOR
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CPU
Output
Devices
Storage
Devices
Input
Devices
Memory
CPU
Output Devices
Storage
Devices
Input Devices Memory

MEMORY:
Memory
Primary or Main
memory
RAM
SRAM
DRAM
ROM
PROM
EPROM
EEPROM
Secondary or
Auxiliary memory
Hard Disk, Floppy Disks,
Magnetic Tapes, Offline
storage, optical disks,
flash memory, USB
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TYPES OF DRAM:
DRAM
Synchronous
DRAM
Enhanced
SDRAM
DDR SDRAM DDR2
Rambus
DRAM
Synchronous
link DRAM
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FUNCTIONAL COMPONENTS OF COMPUTER
 1. Processor:- The processor is an electronic device about a one
inch square, covered in plastic.
 2. Memory:- The processor performs all the fundamental
computations of the computer system.
 3. Input & Output Devices:- Input & Output devices allow the
computer system to interact with the outside world by moving
data into & out of the system.
 4. Storage Devices:- There are two types of storage devices used
with computers: a primary storage device, such as RAM, and a
secondary storage device, like a hard drive. Secondary storage
can be removable, internal, or external storage.
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CLASSIFICATION OF COMPUTERS
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Computers
Analog Digital Hybrid (Analog +Digital)
Purpose Performance& Size
Special Purpose
General Purpose
Embedded Micro Mini Mainframe Super

 Classification of Computers
 1. Analog Computer:-
 Analog computers are used to process continuous data.
 Analog computers represent variables by physical quantities.
 such as flow, temperature, pressure.
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 2. Digital Computer:-
 Digital computer represents physical quantities with the help of digits or
numbers.
 These numbers are used to perform Arithmetic calculations and also
make logical decision to reach a conclusion, depending on, the data
they receive from the user.
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 3. Hybrid Computers
 Various specifically designed computers are with both digital and
analog characteristics combining the advantages of analog and digital
computers when working as a system.
 Hybrid computers are being used extensively in process control system.
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 SUPER COMPUTER
 It is used for large purpose works.
 Used for scientific research.
 Used in research laboratories.
 These computers are extremely expensive and the speed is
measured in billions of instructions per seconds.
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 MINI COMPUTERS
 Mini Computers are smaller in size as well as speed.
 They are versatile that they can be fitted where ever they are needed.
 Their speeds are rated between one and fifty million instructions per
second (MIPS).
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 MICRO COMPUTERS
 These are the smallest range of computers.
 less storing space and processing speed.
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 Applications of Computers:- Today computers are widely used in fields such as
engineering, health care, banking, education, etc.
 Word Processing
 Internet
 Digital Video or Audio composition
 Desktop Publishing
 e- business
 Bioinformatics
 Health Care
 Meteorology
 Multimedia & Animation
 Travel & Tourism
 Simulation
 Robotics
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Introduction to Operating System
 The Interaction between the user and the system is known as Operating
System.
 It provides a user-friendly environment in which a user may easily
develop and execute programs.
 The OS manages these following resources and allocates them to
specific programs and users.
 Processor Management
 Memory Management
 File Management
 Device Management
 Concurrency Control
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Application Programs
System Programs
Operating System
Machine Language
Hardware
Position of Operating System

 Types of OS: DOS, WINDOWS, LINUX and ANDRIOID
 DOS:- Disk Operating System(1981)
 It is a non-graphical command line operating system.
 It was very powerful OS of that time
 Easy to load and install.
 The following are the commands used frequently-
 CD- to change the current directory
 COPY- to copy a file
 DEL- to delete a file
 DIR- to list directory contents
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 EDIT- to start an editor to create or edit text files
 FORMAT- to format a disk
 HELP- to display information about a command
 MKDIR- to create a new directory
 RD- to remove a directory
 REN- to rename a file
 TYPE- to display contents of a file on the screen
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WINDOWS
 Developed by Microsoft.
 Initially two editions were taken- Home Users & IT Professionals.
 IT Professionals.
--Well suited for server environment.
--Limited multimedia features.
--Enhanced networking capability & security.
 Home Users support-
--More functionalities & multimedia features
--Limited support for security & networking
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S.No Version Year Reason/Limitations
1. Version 1.0 1985 Lack of functionality
2. Version 2.0 1987 Slightly more popularity
3. Version 2.03 1988 Different look
4. Version 3.0 1990 Commercial success, user interface
5. Version 3.1 1992 Offered OS a new facelift
6. Windows NT 1993 Designed for professional platform
7. Windows 95 1995 Support for pre-emptive multitasking
8. Windows 98 1998 Slower & less reliable than its previous one
9. Windows 00 2000 Consumer version
10. Windows XP 2001 Very popular.
11. Windows 7 2009 New features, compatibility with H/W
12. Windows 8 2012 Start screen-launch programs, search files,
browse the web.
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 LINUX
 It is very powerful, free, open-source operating system based on UNIX.
 It is free to download and one can make change to it.
 Some advantage includes-
--Low cost
--Stability
--Performance
--Networking, Security
--Flexibility, Multitasking
--Compatibility
--Fast & easy to install
--Better use of hard disk
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 ANDROID
 It is Google’s OS, used on mobile devices.
 Leading smartphones manufacturers such as Samsung, HTC, Motorola.
 Currently it is one of the top operating systems.
 Open source OS powered by the Linux Kernel.
 Users can use this OS to develop apps.
 It is a multitasking OS.
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 PURPOSE
 To provide interaction b/w user and system.
 To manage the computer hardware.
 Provides a user interface.
 To manage process management.
 To organize memory management.
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 FUNCTION, SERVICES and TYPES
 Function & Services
 Functions are little bit same as the services.
 The OS protects stored information from malicious users.
 The OS allows users to create, copy, delete, and rename files.
 Memory management is one of the important function of OS.
 Multiple processes can be executed at the same time.
 With the help of icons it is easy to interact for users.
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TYPES OF OPERATING SYSTEMS
 Based on usage and requirements, OS can be classified into different categories.
 Batch operating system(BOS)
 Single –user single-tasking operating system(SUSTOS)
 Single-user multitasking operating system(SUMOS)
 Multi-user multitasking operating system(MUMOS)
 Multiprocessing(MP)
 Real-time operating system(RTOS)
 Network operating system(NOS)
 Time-sharing operating system(TSOS)
 Distributed operating system(DOS)
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 BOS:
 IT allows very limited interaction between user & processor.
 Programs are bundled as a “batch” and executed together.
 On large data, it performs very well.
 Its processing is performed automatically.
 The problems with Batch Systems are as follows −
--Lack of interaction between the user and the job.
--CPU is often idle, because the speed of the mechanical I/O devices is slower than the
CPU.
--Difficult to provide the desired priority.
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 SUSTOS:
 It allows only one program to execute at a time.
 Example- the Palm OS for Palm handled computers.
 SUMOS:
 Allows single user to perform several tasks simultaneously.
 We usually use this in desktop and laptop computers.
 Example- typing in Ms-Word while listening a song & downloading a file from the
Internet.
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 MUMOS:
 It enables multiple users on different computers to access a single system.
 By one CPU and one OS, many terminals can connect to the main computer.

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 MP:
 It means two or more processors(CPUs) within a single computer system.
 Complex programs can be divided into smaller programs.
 Multiplicity of the processors and how they do act together are transparent to the others.
 Following are some advantages of this type of system:-
--Enhanced performance
-- Execution of several tasks by different processors concurrently, increases the
system's throughput without speeding up the execution of a single task.
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 RTOS
 It guarantees the maximum time for critical operations and complete them on time.
 Real-time systems are used when there are rigid time requirements.
 It is referred to as Hard Real-Time Operating Systems.
 Hard real-time systems guarantee that critical tasks complete on time.
 RTOS are used to control machinery, scientific instruments and industrial systems.
 Soft real-time systems are less restrictive.
 For example, multimedia, virtual reality, Advanced Scientific Projects like undersea
exploration and planetary rovers, etc.
 Some more examples, Scientific experiments, medical imaging systems, industrial
control systems, weapon systems, robots, air traffic control systems, etc
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 NOS
 It runs on a server.
 It provides the server the capability to manage data, users, groups,
security, applications, and other networking functions.
 It allows shared file and printer access among multiple computers in
a network.
 Examples of network operating systems include Microsoft Windows
Server 2003, Microsoft Windows Server 2008, UNIX, Linux, Mac OS X,
Novell NetWare, and BSD.
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 Advantages of network operating systems:
--Centralized servers are highly stable.
--Security is server managed.
 Disadvantages
 High cost of buying and running a server.
 Dependency on a central location for most operations.
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TSOS
 time sharing systems are an extension of multiprogramming systems.
 the prime focus is on minimizing the response time.
 Multiple jobs are executed by the CPU by switching between them.
 i.e the user can receive an immediate response.
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Advantages Disadvantages
Provides the advantage of quick
response.
Question of security and integrity of
user programs and data.
Avoids duplication of software. Problem of reliability.
Reduces CPU idle time. Problem of data communication.

 DOS
 It use multiple central processors to serve multiple real-time applications
and multiple users.
 Processors communicate with one another through various
communication lines (such as high-speed buses or telephone lines).
 These are referred as loosely coupled systems or distributed systems.
 These processors are referred as sites, nodes, computers, and so on.
 Advantages
 Better service to the customers.
 Reduction of the load on the host computer.
 Reduction of delays in data processing.
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NUMBER SYSTEM: BINARY, OCTAL, DECIMAL AND
HEXADECIMAL
Data is stored in a computer in the form of 0s & 1s.
A number is represented by a string of digits, where each digit position has an associated
weight.
Each number system is associated with a base or radix.
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System Base Symbols
Used by
humans?
Used in
computers?
Decimal 10 0, 1, … 9 Yes No
Binary 2 0, 1 No Yes
Octal 8 0, 1, … 7 No No
Hexadecimal 16 0, 1, … 9,A, B,..F No No

BINARY:
 1. Convert 1101 into a decimal number.
Decimal number = 1*23 + 1*22 + 0*21 +1*20
= 1 * 8 + 1* 4 + 0 +1*1
= 8 + 4+ 0+ 1
= 13.
2. Convert (13)10 into a binary number.
13/2 = 6 rem 1
6/2 = 3 rem 0
3/2 = 1 rem 1
1/2 = 1 rem 1
(13)10 =(1101)2
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OCTAL:
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 The octal number system: Base-8
 Eight digits: 0,1,2,3,4,5,6,7
 The hexadecimal number system: Base-16
 Sixteen digits: 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F
 For our purposes, base-8 and base-16 are most useful as a
“shorthand” notation for binary numbers
10
1012
8 )5.87(84878281)4.127(  
10
0123
16 )46687(16151651661611)65(  
FB

NUMBERS WITH DIFFERENT BASE:
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Decimal Binary Octal Hex
0 0000 0 0
1 0001 1 1
2 0010 2 2
3 0011 3 3
4 0100 4 4
5 0101 5 5
6 0110 6 6
7 0111 7 7
8 1000 10 8
9 1001 11 9
10 1010 12 A
11 1011 13 B
12 1100 14 C
13 1101 15 D
14 1110 16 E
15 1111 17 F

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 Converting from octal to binary: Replace each octal digit with its
equivalent 3-bit binary sequence
 Converting from binary to octal: Make groups of 3 bits, starting from
the binary point. Add 0s to the ends of the number if needed. Convert
each bit group to its corresponding octal digit.
= 6 7 3 . 1 2
= 110 111 011 . 001 010
=
8)12.673(
2)001010.110111011(
10110100.0010112 = 010 110 100 . 001 0112
= 2 6 4 . 1 38

BINARY AND HEX CONVERSIONS
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 Converting from hex to binary: Replace each hex digit with its
equivalent 4-bit binary sequence
 Converting from binary to hex: Make groups of 4 bits, starting
from the binary point. Add 0s to the ends of the number if
needed. Convert each bit group to its corresponding hex digit.
261.3516 = 2 6 1 . 3 516
= 0010 0110 0001 . 0011 01012
10110100.0010112 = 1011 0100 . 0010 11002
= B 4 . 2 C16

BINARY ARITHMETIC:
 Rules of Binary Addition
 0 + 0 = 0, 0+1 = 1, 1+0 = 1
 1+1 = 0, and carry 1 to the next more significant bit.
 Rules of Binary Subtraction
 0 - 0 = 0, 1-0 = 1, 1-1 = 0
 0-1= 0, and borrow 1 from the next more significant bit.
 Rules of Multiplication
 0 * 0 = 0, 1*0 = 0, 1*1 = 1, 0*1= 0
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BASICS OF PROGRAMMING:
 Program is a set of instruction to solve the problem.
 ‘C’ has now become a widely used professional language for
various reasons.
 Easy to learn
 Structured language
 It produces efficient programs.
 It can handle low-level activities.
 It can be compiled on a variety of computers.
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SOME FACTS ABOUT “C”
 C was invented to write an operating system called UNIX.
 C is a successor of B language which was introduced around
1970
 The language was formalized in 1988 by the American National
Standard Institute (ANSI).
 By 1973 UNIX OS almost totally written in C.
 Today C is the most widely used System Programming Language.
 Most of the state of the art software have been implemented
using C.
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WHY TO USE “C”
 C was adopted as a system development language.
 It produces code that runs nearly as fast as code written in assembly
language.
 Some examples of the use of C might be:
 Operating Systems Language Compilers
 Assemblers Text Editors
 Print Spoolers Network Drivers
 Modern Programs Data Bases
 Language Interpreters Utilities
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APPROACHES TO PROBLEM SOLVING
 People who are really good at solving problems go
about it systematically.
 They have a way of placing the problem in context.
 They don't jump to conclusions.
 They evaluate alternatives.
 A good way to become a systematic problem solver is
to adopt the following five-step problem-solving
process.
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IDENTIFY THE PROBLEM.
 This is critical: you must try to solve the right
problem.
 Identify the right problem by asking the right
questions and observing.
 You cannot identify the customer's problems
by presenting your products.
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ANALYZE THE PROBLEM.
 How often does the problem occur?
 How severe is it?
 Are there any special circumstances that are
present when it occurs?
 What might be the causes of the problem?
 Can you rule out any causes?
 How long has it been going on?
 Has it gotten worse?
 How is the problem affecting other processes or people?
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ANALYZE PROBLEM
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IDENTIFY DECISION CRITERIA.
 How will you and the customer make decisions when it is time to
decide?
 How will you weigh the criteria?
 Can you identify independent standards that can be used?
62

DEVELOP MULTIPLE SOLUTIONS.
 Don't stop at the first solution that you or others identify.
 It may be good, but much better ones may exist.
 Evaluate alternative scenarios.
 As objectively as possible, assess the pros and cons of each.
Choose the optimal solution.
 Use the criteria you developed in the third step of this problem-
solving process to choose the best solution.
 Develop a base of support that will ensure you can implement
the solution.
 Prepare for contingencies.
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CONCEPT OF ALGORITHM AND FLOWCHARTS
 The sequence of steps to be performed in order to solve a
problem by the computer is known as an algorithm.
 Three reasons for using algorithms are efficiency, abstraction and reusability.
 Flowchart is a diagram that shows the step-by-step execution of a control
structure.
 Flowchart is a graphical or symbolic representation of an algorithm.
 It is the diagrammatic representation of the step-by-step solution to a given
problem.
 A diamond-shaped box represents a decision.
 A rectangular box represents an assignment statement or a process.
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EXAMPLE OF ALGORITHM
 Write an algorithm to add two numbers.
 STEP1 Read the Value of A and B.
 STEP2 SUM = A+B.
 STEP3 Display SUM.
 STEP4 Stop.
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EXAMPLE OF A FLOWCHART
 Write (Display) the Sum, Average and Product
 Flowchart for the above problem will look like
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Start
Read X,Y,Z
S= X+Y+Z
A=S/3
P=X*Y*Z
Write S,A,P
Stop

ADVANTAGES OF USING FLOWCHARTS:
 Communication: Flowcharts are better way of communicating
the logic of a system to all concerned.
 Effective analysis: With the help of flowchart, problem can be
analyzed in more effective way.
 Proper documentation:Program flowcharts serve as a good
program documentation, which is needed for various purposes.
 Efficient Coding: The flowcharts act as a guide or blueprint
during the systems analysis and program development phase.
 Proper Debugging: The flowchart helps in debugging process.
 Efficient Program Maintenance:The maintenance of operating
program becomes easy with the help of flowchart. It helps the programmer to
put efforts more efficiently on that part.
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Example Of A If-else Flowchart
68

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Start
Read A, B
Is A > B
Print A Print B
End
Yes No
Flow Chart to find largest of two numbers:

LIMITATIONS OF USING FLOWCHARTS:
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 Complex logic: Sometimes, the program logic is quite complicated. In
that case, flowchart becomes complex and clumsy.
 Alterations and Modifications: If alterations are required the flowchart
may require re-drawing completely.
 Reproduction: As the flowchart symbols cannot be typed,
reproduction of flowchart becomes a problem.

TYPES OF COMPUTER LANGUAGES: MACHINE,
ASSEMBLY, & HIGH LEVEL LANGUAGES
 A programming language is an artificial language that can be
used to control the behavior of a machine, particularly a
computer .
 Programming languages, like human languages, are defined
through the use of syntactic and semantic rules, to determine
structure and meaning respectively.
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MACHINE LANGUAGE:
72
• It is the lowest-level programming language.
Machine languages are the only languages understood by
computers.

ASSEMBLY LANGUAGE:

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 An assembly language is a low-level language for programming computers.
 The word "low" does not imply that the language is inferior to high-level
programming languages but rather refers to the small or nonexistent amount of
abstraction between the language and machine language, because of this, low-level
languages are sometimes described as being "close to the hardware."
 It implements a symbolic representation of the numeric machine codes and other
constants needed to program a particular CPU architecture.

HIGH LEVEL LANGUAGE:
 High-level languages are relatively easy to learn because the
instructions bear a close resemblance to everyday language,
and because the programmer does not require a detailed
knowledge of the internal workings of the computer.
 Each instruction in a high-level language is equivalent to several
machine-code instructions, therefore it is more compact than
equivalent low-level programs.
 High-level languages are used to solve problems and are often
described as problem-oriented languages
74

Concept of Assembler
 It translates the assembly language into machine level language.
 Translate mnemonic operation codes to machine code.
 Assign addresses to symbolic labels used by the programmer
Fig1. The flow of assembler
75
Assembler
Assembly language code Object code

COMPILER:
 It is a program translator that translates the instruction of a higher level
language to machine language.
 It is called compiler because it compiles machine language instructions for
every program instructions of higher level language.
 The programs written by the programmer in higher level language is called
source program.
 After this program is converted to machine languages by the compiler it is called
object program.
76

INTERPRETER:
 An interpreter is another type of program translator used for translating
higher level language into machine language.
 It takes one statement of higher level languages, translate it into machine
language and immediately execute it.
 Translation and execution are carried out for each statement.
 It differs from compiler, which translate the entire source program into
machine code.
77
High level
language interpreter
Low level
language

LOADER:
 Software that copies programs
from a storage device to the
main memory, where they can be
executed.
 A loader is a special type of
program that is part of an OS.
78
Object code
source code
Assembly code
Executable code
compiler
Preprocessor
assembler
Link editor
libraries

LINKER:
 Software that transforms source code written in a programming language into
machine language comprising of just two digits, 1 & 0.
 It is also called link editor and binder.
 It combines object modules to form an executable program.
 TRANSLATOR:
 A computer program, which translates a code written in one programming
language to a code in another language that the computer understands.
79

UNIT-2 STANDARD I/O IN “C”
 When we say Input, it means to feed some data into a program.
 When we say Output, it means to display some data on screen, printer, or in
any file.
 The Standard Files
 C programming treats all the devices as files.
80
Standard File File Pointer Device
Standard input stdin Keyboard
Standard output stdout Screen
Standard error stderr Your screen

STANDARD I/O IN “C”
 Two commonly used functions for I/O (Input/Output) are printf() and
scanf().
 The scan() function reads formatted input from standard input (keyboard).
 The printf() function sends formatted output to the standard output
(screen).
 #include <stdio.h> //This is needed to run printf() function.
int main() {
printf(“ C programming”); // displays the content inside quotation.
return 0;
}
OUTPUT
C programming
81

TYPES AND THEIR VALUES
82
Predefined Types Values
Read Character from File getc, fgetc and getchar
Write Character to File putc, fputc and putchar
Read String from File fgets and gets
Read Binary Data from File fread
Write String to File fputs and puts
Write Binary Data to File fwrite
Read Formatted Input scanf, fscanf, sscanf
Write Formatted Output printf, fprintf, sprintf
File Position fgetpos, fsetpos, rewind, fseek, and ftell

FUNDAMENTAL DATA TYPES:
 A data type is--
 A set of values AND.
 A set of operations on those values.
 A data type is used to--
 Identify the type of a variable when the variable is declared.
 Identify the type of the return value of a function.
 Identify the type of a parameter expected by a function.
83

FUNDAMENTAL DATA TYPES:
 void – used to denote the type with no values
 int – used to denote an integer type
 char – used to denote a character type
 float, double – used to denote a floating point
type
 int *, float *, char * – used to denote a pointer
type, which is a memory address type.
84

TWO CLASSIFICATIONS OF DATA TYPES
 Built-in data types
 Fundamental data types (int, char, double, float,
void, pointer)
 Derived data types (array, string, structure)
 Programmer-defined data types
 Structure
 Union
 Enumeration
85

DERIVED DATA TYPES:
 Array – a finite sequence (or table) of variables of the same data
type
 String – an array of character variables
 Structure – a collection of related variables of the same and/or
different data types. The structure is called a record and the
variables in the record are called members or fields
86

PRIMARY DATA TYPES
87
PDT(Integer)
Signed
int
Short int
Long int
Unsigned
Unsigned
int
Unsigned
short int
Unsigned
long int

SINGLE AND DOUBLE FLOATING POINT
88
Floating point type
float
double
Long
double

CHARACTER:
89
Character
char
Signed char
Unsigned
char

SIZE & RANGE OF DATA TYPES:
Type Size(bits/bytes) Range
Char or signed char 8/1 -128 to 127
Unsigned char 8/1 0 to 255
int or signed int 16/2 - 32768 to 32767
Unsigned int 16/2 0 to 65535
Short int or
Signed short int 8/1 -128 to 127
Unsigned short int 8/1 0 to 255
Long int or
Signed long int 32/4 -2147483648 to 2147483647
Unsigned long int 32/4 0 to 4294967295
float 32/4 3.4 E- 38 to 3.4 E + 38
double 64/8 1.7 E – 308 to 1.7 E + 308
Long double 64/8 3.4 E- 4932 to 3.4 E + 4932
90

STORAGE CLASSES: AUTOMATIC, REGISTER, STATIC
AND EXTERNAL
 A storage class defines the scope (visibility) and life time of
variables and/or functions within a C Program.
 There are following storage classes which can be used in a C
Program
• Auto (automatic variables)
• Register variables
• Static variables
• Extern(external variables)
91

AUTO - STORAGE CLASS
 auto is the default storage class for all local variables.
{
 int Count;
 auto int Month;
}
 The example above defines two variables with the same storage
class. auto can only be used within functions, i.e. local variables.
92

AUTO - STORAGE CLASS
 Formal parameters and local variables of functions are variables
that are automatically allocated on the stack when a function is
called and automatically deallocated when the function returns.
 They are of storage class auto.
 By default they are assigned garbage value by the compiler.
 Example
 void main()
{
int detail; or
auto int detail; //Both are same
}
93

REGISTER - STORAGE CLASS
 register is used to define local variables that should be stored in a
register instead of RAM. This means that the variable has a
maximum size equal to the register size (usually one word) and
cant have the unary '&' operator applied to it (as it does not
have a memory location).
{
register int Miles;
}
 Register should only be used for variables that require quick
access - such as counters.
94

REGISTER VARIABLES
 If you declare a variable of type register, it simply alerts the
compiler to the fact that this memory cell will be referenced
more often than most.
 Register is a special high-speed memory location inside the
central processor.
 Syntax :
register int number;
95

STATIC VARIABLES:
 Static variable is allocated and initialized one time, prior to
program execution.
 It remains allocated until the entire program terminates.
 A static variable tells the compiler to persist the variable until the
end of program.
 static is initialized only once and remains into existence till the
end of program.
 Scope of internal static variable remains inside the function in
which it is defined.
 External static variables remain restricted to scope of file in each
they are declared.
 They are assigned 0 (zero) as default value by the compiler.
96

EXAMPLE: STATIC VARIABLE
 void test(); //Function declaration
main() {
test(); test(); test();
} void test() {
static int a = 0; //Static variable
a = a+1;
printf("%dt", a); }
 output :
1 2 3
97

EXTERNAL VARIABLES
 The extern keyword is used before a variable to inform the
compiler that this variable is declared somewhere else.
 The extern declaration does not allocate storage for variables.
 A variable that is declared outside any function is a Global
variable.
 Problem when extern is not used
 main()
{
a = 10; // Error: cannot find variable a
printf("%d", a);
}
98

EXTERN:
 Storage class of names known to the linker.
 Example: extern int square (int x);
 Means the function will be available to the linker.
 It notifies the compiler that such a function exists and that the
linker will know where to find it.
 int number;
void main() {
number=10; }
fun1() {
number=20; }
fun2() {
number=30; } Here the global variable number is available to all
three functions.
99

OPERATORS AND EXPRESSIONS:
 Operators form expressions by joining individual constants, variables, array elements.
 Operators are symbols which take one or more operands or expressions and perform
arithmetic or logical computations.
 C includes a large number of operators which fall into different categories.
 These operators are used to form expressions. Some operators are as follows-
 --arithmetic operators,
--unary operators,
--relational and logical operators,
--assignment operators and the
--conditional operators
100

OPERATOR PRECEDENCE:
 Consider the following arithmetic operation:
- left to right
6 / 2 * 1 + 2 = 5
- right to left
6/2 * 1 + 2 = 1
- using parentheses
= 6 / (2 * 1) + 2
= (6 / 2) + 2
= 3 + 2
= 5
101

USING NUMERIC AND RELATIONAL OPERATORS:
 --Arithmetic operators:
 There are five main arithmetic operators in ‘C’.
 They are ‘+’ for additions,
 ‘-' for subtraction,
 ‘*’ for multiplication,
 ‘/’ for division and
 ‘%’for remainder after integer division.
 This ‘%’ operator is also known as modulus operator.
102

ARITHMETIC OPERATORS:
Operator example Meaning
+ a + b Addition –unary
- a – b Subtraction-
unary
* a * b Multiplication
/ a / b Division
103

EXAMPLE OF ARITHMETIC OPERATOR
 Operands can be integer quantities, floating-point quantities or
characters.
 Example m=30 & n=20 respectively , now performing addition,
subtraction, multiplication, division, and modulus on m& n, we
get…….
 m+n=50
 m-n=10
 m*n=600
 m/n=1
 m%n=10
104

UNARY OPERATORS:
 ‘C’ includes a class of operators that act upon a single operand
to produce a new value.
 Such operators are known as unary operators.
 Unary operators usually precedes their single operands,
though some unary operators are written after their operands.
 The most common unary operator is unary minus, where a minus
 sign precedes a numerical constant, a variable or an expression.
 e.g. -5,-10, -20(numbers)
 x=-y(variable)
105

MIXED OPERANDS:
 When one of the operands is real and the other is integer.
 If either operand is of the real type, then only the real operation is
performed .
 Then the result is always a real number.
 Example ---
15 / 10.0 = 1.5
Whereas
15 / 10 = 1.
106

TYPE CONVERSION:
 Type conversion is done when the expression has variables of
different data types.
 The data type is promoted from lower to higher level.
 Type conversion is automatically done when the value is assign.
 The hierarchy of data types (from higher to lower) is shown as:
107

CONVERSION HIERARCHY OF DATA TYPES
108
Long
double
double
int
short
float
Unsigned long
int
Long int
unsigned int
char

EXAMPLE1
 Consider the code given below
 float x;
 int y= 3;
 x=y;
 Now here integer value is promoted to float.
 This is known as promotion.
109

EXAMPLE2
 Now, x= 3.0, as automatically integer value is converted into its
equivalent floating point representation.
 Consider the following group of statements:
 float f= 3.5;
 int i;
 i= f;
 Statement i= f results in f to be demoted to type int,
 the fractional part of f will be lost and I will contain 3 (not 3.5).
110

RELATIONAL OPERATORS:
Operator Meaning
< Is less than
<= Is less than or equal to
> Is greater than
>= Is greater than or equal
to
== Equal to
!= Not equal to
111

LOGICAL OPERATORS:
 For relational expression, 0 is FALSE, 1 is TRUE.
 Any numeric value is interpreted as either TRUE or FALSE when it is used in a C /
C++ expression or statement that is expecting a logical (true or false) value. The rules
are:
1. A value of 0 represents FALSE.
2. Any non-zero (including negative numbers) value represents TRUE.
112
Operator Meaning
&& Logical AND
|| Logical OR
! Logical NOT

LOGICAL OPERATORS:
Expressions Evaluates as
(3 == 3) && (4 != 3)
True (1) because both operands are
true
(4 > 2) || (7 < 11)
True (1) because (either) one
operand/expression is true
(3 == 2) && (7 == 7) False (0) because one operand is false
! (4 == 3)
True (1) because the expression is
false
(3 == 3) && (4 != 3)
True (1) because both operands are
true
NOT(FALSE) = TRUE
NOT(TRUE) = FALSE
113

BIT OPERATORS:
 A bit is the smallest digit capable of being stored in a modern day digital
computer.
 A byte, consisting of 8 bits is the smallest unit of storage that a computer can work
with.
 A word ( usually somewhere between 32 and 64 bits) is the smallest addressable
item in a computer.
---The word size of a computer is usually dictated by either the bus size of the
system or the word size of the CPU.
114

BITWISE OPERATORS:
Operator Name Description
& bitwise AND 1 only if both operands are 1.
| bitwise OR 1 if ether or both operands are
1
^ bitwise exclusive or 1 if either but not both
operands are 1
<< Left Shift Shifts bits of the first operand
by the number of bits specified
by the second operand.
>> Right Shift Shifts bits of the first operand
by the number of bits specified
by the second operand.
~ Complement Flips the bits in the operand.
All 1’s become 0’s and all 0’s
become 1’s.
115

BITWISE OPERATORS:
 Bitwise operators are used to directly manipulate the
bits of integral operands such as char, short, int, long
(both signed and unsined).
 Normally unsigned integers are used when dealing
with bitwise operations.
116

ASSIGNMENT OPERATORS:
 The compound assignment operators consist of a binary operator and
the simple assignment operator.
 They perform the operation of the binary operator on both operands
and store the result of that operation into the left operand.
 The following table lists the simple and compound assignment
operators and expression examples:
117

Simple Assignment Operator
=
 The simple assignment operator has the following form:
lvalue = expr
 The operator stores the value of the right operand expr in the
object designated by the left operand lvalue.
 The left operand must be a modifiable lvalue.
 The type of an assignment operation is the type of the left
operand.
i = 5 + x;
118

CONDITIONAL OPERATORS:
Syntax:
exp1 ? exp2 : exp3
Where exp1,exp2 and exp3 are expressions
Working of the ? Operator:
Exp1 is evaluated first, if it is nonzero(1/true) then the expression2 is evaluated
and this becomes the value of the expression,
If exp1 is false(0/zero) exp3 is evaluated and its value becomes the value of the
expression
Ex: m=2;
n=3
r=(m>n) ? m : n;
31-Dec-16
ANKUR SRIVASTAVA ASSISTANT PROFESSOR JETGI
119

OPERATOR PRECEDENCE AND ASSOCIATIVELY :
 The operator within C are grouped hierarchically according to their order of evaluation
known as precedence.
 operations with a higher precedence are carried out before operations having a lower
precedence.
 Arithmetic operators *,/ and % are under one precedence group and
 +,- are under another precedence group.
 The operators *, / and % have higher precedence than + and -.
120

 Consecutive operations within the same precedence group are
carried out. This is known as associativity.
 Example, say there are 3 variables a, b, and c having values 5,10
and 15 respectively.
 The different operations on these three variables and their result is
as follows:
 a+b/c=5,
 b*c-a=145
 a*b/c= 3,
 (a+c)*b/a=40
121

OPERATOR PRECEDENCE:
Precedence and Associativity of C Operators
Symbol Type of Operation Associativity
[ ] ( ) . –> postfix ++ and
postfix ––
Expression Left to right
prefix ++ and prefix –– sizeof
& * + – ~ !
Unary Right to left
typecasts Unary Right to left
* / % Multiplicative Left to right
+ – Additive Left to right
<< >> Bitwise shift Left to right
< > <= >= Relational Left to right
== != Equality Left to right
& Bitwise-AND Left to right
^ Bitwise-exclusive-OR Left to right
122

OPERATOR PRECEDENCE EXAMPLE
 Evaluating expressions using the precedence chart
123
1. x= 3 * 4 + 5 * 6
=12 + 5 * 6
=12 + 30
=42
2. x = 3 * ( 4 + 5) * 6
= 3 * 9 * 6
= 27 * 6
= 162
3. x= 3 * 4 % 5 / 2
= 12 % 5 / 2
= 2 / 2
= 1
4. x= 3 * (( 4 % 5) / 2 )
= 3 * (4 / 2)
= 3 * 2
= 6

FUNDAMENTALS OF C PROGRAMMING:
 C was developed in 1972 by “Dennis Ritchie” at AT & T Bell Lab.
 It was developed for the ease of programming.
 Some features for which it is so popular:
---It is very calm to learn
---It is a planned language
---It produces well-organized programs.
---It can handle low-level activities.
---It can be compiled on a multiplicity of computers.
124

STRUCTURE OF C PROGRAM
 An example of simple program in C
#include <stdio.h>
void main(void)
{
printf(“I love programmingn”);
printf(“You will love it too once ”);
printf(“you know the trickn”);
}
125
Preprocessor directive
Null Data Type
Closing parenthesis
Angle bracket
Standard input output
function
Line termination

WRITING AND EXECUTING THE FIRST C PROGRAM
 #include<stdio.h>
 #include<conio.h>
 Void main()
 {
 clrscr();
 Int a, b, c;
 Printf(“enter the value of a &
b”);
 Scanf(“%d %d”, &a, &b);
 c= a+b;
 Printf(“value of c is =%d”, c);
 getch();
 }
OUTPUT
Enter the value of a & b
5 5
10
126

COMPONENTS OF C LANGUAGE
 Some basic component of a C program.
 #include - The #include is known as a preprocessor directive
It is used to tell the C preprocessor to find the stdio file with
extension .h.
 main() – Execution of a program starts from a main() function.
 printf() - This is the standard way of producing output.
The functionality of printf() is referenced in stdio.h by the C
compiler.
 scanf() - This is the standard way of taking input from user.
 comments: Comments are information given by the program to make
a program readable and easy to understand.
127

STANDARD I/O IN C
 So far our C programs are as follows:
/* description of program */
#include <stdio.h>
/* any other includes go here */
int main(){
/* program body */
return 0;
}
128

UNIT-3 CONDITIONAL PROGRAM EXECUTION
 C supports two types of decision control statements.
129
Selection/Branching
statement
Conditional
type
if If-else If-else-if switch
Unconditional
type

CONDITIONAL BRANCHING STATEMENTS:
 These statements helps to jump from one part to another part.
 Whether a particular condition is satisfied or not.
 It includes:-
---- if statement
---- if- else statement
---- if- else- if statement
---- Switch statement
130

IF STATEMENTS
 The if statement allows the program to test the state of the
program variables using a Boolean expression.
 Syntax
If (test expression)
{
Statement 1;
……………
Statement n;
}
Statement x;
131
Test
exp
Statement
block 1
Statement x
FALSE
TRUE

IF-ELSE STATEMENT
 The if-else statement expresses simplest decision making.
 The syntax is
if (expression)
statement1
elseopt
Statement2
132

IF –ELSE STATEMENT
133

NESTED IF-ELSE
 When the if-else condition exists in another if-else condition, it is nested if-else.
 Syntax
If (test condition-1)
{
if (test condition-2)
{
Statement-1; }
else {
Statement-2; }
}
else
{
Statement-3;
}
Statement- x;
134

IF-ELSE-IF STATEMENT
 For testing additional conditions if-else-if statements is
constructed.
If (condition-1)
Statement -1;
Else if (condition-2)
Statement-2;
Else if (condition-3)
Statement-3;
Else if (condition-n)
Statement –n;
Else
Default-statement;
Statement-x;
135

SWITCH STATEMENTS
136

SWITCH STATEMENT
 The switch statement is used to select one of several alternatives when
the selection is based on the value of a single variable or an expression.
switch (controlling expression) {
case label1:
statement1
break;
case label2:
statement2
break; ……..
case labeln:
statementn
break;
default:
statementd; }
137
If the result of this controlling expression
matches label1, execute staement1 and then break
this switch block.
If the result matches none of all labels, execute the
default statementd.

USE OF BREAK AND DEFAULT WITH SWITCH
Switch (exp)
{
case value-1:
block-1
break;
case value-2:
block-2
break;
…………….
…………….
default:
default-block
break; } statement-x;
138

PROGRAM LOOPS AND ITERATIONS:
 In looping, a sequence of statements are executed until some
conditions for termination of the loop are satisfied.
 Two segments are:
------- body of the loop
------- control statement
Depending on the position of the control statement in the loop,
A control structure may be either—
-------- entry controlled loop or
-------- exit controlled loop.
139

LOOP CONTROL STRUCTURES
140
True
Test
condition
?
Test
condition
?
Body of the
loop
Body of the
loop
False
False
True
EntryEntry
(b) Exit controlled loop(a) Entry controlled loop

USE OF WHILE:
THE WHILE STATEMENT IS USED TO REPEAT A COURSE OF ACTION.
141

THE WHILE STATEMENT
142
Format
While (test condition)
{
Body of the loop
Syntax
Statement x;
While (condition)
{
statement block;
}
Statement y;
WAP to calculate the sum
of first 10 nos.
int i= 1, sum= 0;
while(i<=10)
{
sum = sum +1;
i= i+1;
}
printf(“n sum =% d”, sum);
return 0;
}
OUTPUT
Sum= 55

DO WHILE
DO STATEMENT
 The do statement is a variant of the while statement that tests its
condition at the bottom of the loop.
General Form of the do Statement-
do
statement
while (expr);
next statement
143
do
{
body of the loop
}
while (test-condition);

EXAMPLE OF DO-WHILE STATEMENT
144
int i =1;
do
{
printf(“n % d”, i);
i=i+1;
}
while(i<=10);
return 0;
}
The code will print nos
from 1 to 10.

COMPARISON B/W WHILE, DO, FOR
WHILE DO FOR
while (...) {
...
continue;
...
cont: ;
}
do {
...
continue;
...
cont: ;
}
for (...) {
...
continue;
...
cont: ;
}
145

FOR LOOPS
146

SYNTAX OF FOR LOOP
 for (initialization ; test-condition ; increment)
{
body of the loop
}
Example
for (i = 1; i<=n ; i++)
{
printf(“n %d”, i);
}
147

MULTIPLE LOOP VARIABLES
 MLV are the loops which can be placed inside other loops.
Example:
………..
………..
while(……..)
{
for(………)
{ …….
……..
if (……..) goto end_of_program;
………
}
………
………
} end_of_program
148
Jumping out
of loops

USE OF BREAK AND CONTINUE STATEMENTS.
 The break statement causes an exit from the innermost enclosing
loop or switch statement.
 The continue statement causes the current iteration of a loop to
stop and the next iteration to begin immediately.
149

DIFFERENCE B/W BREAK & CONTINUE
break continue
while (……)
{
if (condition)
break;
………..
}
……….
Transfers control out of the loop while.
Example
int i = 1;
while (i<= 10)
{
if (i==5)
break;
printf(“n % d”, i);
i=i+1; }
return 0; }
while (……)
{
……….
if (condition)
continue;
………..
}
Transfers control to the condition
expression of the while loop.
Example
int i = 1;
for (i=1; i<=10; i++)
{
if (i==5)
continue;
printf(“t % d”, i);
}
return 0; }
150

THE GOTO STATEMENT
 GOTO is used to branch unconditionally from one point to
another.
 The general forms of goto & label statements are shown below:
151
goto label;
………….
………….
………….
label;
Statement;
label;
statement;
………….
………….
………….
goto label;
Forward jump Backward jump

FUNCTIONS:
 A complex problem is often easier to solve by dividing it into
several smaller parts, each of which can be solved by itself.
 This is called structured programming.
 These parts are sometimes made into functions in C.
 main() then uses these functions to solve the original problem.
152

Main() Function Calls Func1()
153
main()
{
…………
func1();
…………
return 0;
}
func1()
{
Statement block;
}
Main
function
Function A Function B
Function B1 Function B2
Function c

DEFINITION OF FUNCTIONS:
A function definition shall include the following
elements:
1. Function name;
2. Function type;
3. List of parameters;
4. Local variable declarations;
5. Function statements; and
6. A return statement.
154
Function header
Function body

FUNCTIONS WITH ARRAY
 Example, the call
largest (a, n)
Will pass the whole array a to the called function.
The largest function header might look like:
float largest (float array [ ], int size)
The declaration of the formal argument array is made as follows:
float array [ ];
The pair of brackets informs the compiler that the argument array is
as array of numbers.
155

PASSING VALUES TO FUNCTIONS
 Three rules to pass an array to a function:
A. The function must be called by passing only the name of the
array.
B. In the function definition, the formal parameter must be an array
type; the size of the array does not need to be specified.
C. The function prototype must show that the argument is an array.
156

RECURSIVE FUNCTIONS
Recursion: the ability of a subprogram to call itself.
 Each recursive solution has at least two cases
 base case: the one to which we have an answer
 general case: expresses the solution in terms of a call to itself with a smaller
version of the problem.
 For example, the factorial of a number is defined as the number times the product of all
the numbers between itself and 0:
N! = N * (N  1)!
157

UNIT-4 ARRAYS
 An array is a named collection of homogeneous items in which
individual items are accessed by their place within the collection.
 An array is a collection of variables of the same type that are referred
to by a common name.
Eg.
 product part numbers:
int part numbers[] = {123, 326, 178, 1209};
 student scores:
int scores[10] = {1, 3, 4, 5, 1, 3, 2, 3, 4, 4};
 characters:
char alphabet[5] = {’A’, ’B’, ’C’, ’D’, ’E’};
158

INITIALIZATION OF ARRAY
 Array – a set of elements all of the same type stored contiguously
in memory – e.g.,
 int A[25]; // 25 integers
 struct Str B[15]; /* 15 objects of
type struct Str */
 double C[]; /* indeterminate #
of doubles */
159

ARRAY NOTATION
160
An array of size N is indexed from zero to N-1
79 87 94 82 67 98 87 81 74 91scores
The entire array
has a single name
Each value has a numeric index
This array holds 10 values that are indexed from 0 to 9

MANIPULATING ARRAY ELEMENTS
 Some other examples of array declarations:
float[] prices = new float[500];
boolean[] flags;
flags = new boolean[20];
char[] codes = new char[1750];
161

2D ARRAY
162
 A one-dimensional array stores a list of elements
 A two-dimensional array can be thought of as a table of
elements, with rows and columns
one
dimension
two
dimensions

3D ARRAY
163
An array can be declared with multiple dimensions.
2 Dimensional 3 Dimensional
Multiple dimensions get difficult to visualize graphically.
•
int [][][] table3 = { { {1,2}, {3,4} },
{ {5,6,7} , {8}, {9,10}
}
};

USING MULTI-DIMENSIONAL ARRAYS
 An array can have many dimensions – if it has more than one
dimension, it is called a multidimensional array
 Each dimension subdivides the previous one into the specified
number of elements
 Each dimension has its own length constant
 Because each dimension is an array of array references, the
arrays within one dimension can be of different lengths
these are sometimes called ragged arrays
164

MULTIDIMENSIONAL ARRAY
 Arrays with more than one index
 number of dimensions = number of indexes
 Arrays with more than two dimensions are a simple extension of
two-dimensional (2-D) arrays
 A 2-D array corresponds to a table or grid
 one dimension is the row
 the other dimension is the column
 cell: an intersection of a row and column
 an array element corresponds to a cell in the table
165

STRUCTURE:
 A structure is a collection of one or more components (members).
 Structures are called records in many other programming languages.
 Members are known as fields.
Declaring a structure:-
struct {
char name[25];
int id, age;
char sex;
} s1, s2;
166

INITIALIZING A STRUCTURE:-
struct {
char name[25];
int id, age;
char sex;
}
s1 = { "Smith, John", 2813, 25, 'M'},
s 2 = { "Smith, Mary", 4692, 23, 'F'};
167

ACCESSING THE MEMBERS OF A STRUCTURE:
 The members of a structure are accessed by writing first the name of the
structure, then a period, then the name of the member:
struct student {
char name[25];
int id, age;
char sex;
} s;
strcpy(s.name, "Doe, John");
s.id = 18193;
s.age = 18;
s.sex = 'M';
168

UNION:
 A union is similar to a structure, except that its members are overlaid
(located at the same memory address).
 A union is like a structure in which all members are stored at the
same address.
 Example:
union {
int i;
double d;
} u;
169

ACCESSING THE MEMBER
 The members of a union are accessed in the same way as members of a
structure:
u.i = 15;
or
u.d = 8.89;
Since u.i and u.d have the same memory address, changing the value of one
alters the value of the other.
170

ENUMERATED DATA TYPES
 Enumeration Data Types
 Declaration
 Assignment
 Operations
 Looping with Enumeration
Types
 A data type is
 A set of values together with
 A set of operations on those
values.
 A name for the data type.
 A set of values for the data
type.
 A set of operations on the
values.
171

UNIT-5 POINTERS
• In a generic sense, a “pointer” is anything that tells us where
something can be found.
– Addresses in the phone book
– URLs for webpages
-- Road signs
What actually ptr is?
 ptr is a variable storing an address
 ptr is NOT storing the actual value of i
172

EXAMPLE OF POINTER
173
 int i = 5; ptr
 int *ptr;
 ptr = &i;
 printf(“i = %dn”, i);
 printf(“*ptr = %dn”, *ptr);
 printf(“ptr = %pn”, ptr);
Output:
i = 5
*ptr = 5
ptr = effff5e0
address of i
5i
value of ptr
= address of
i
in memory

POINTER APPLICATIONS IN C PROGRAMMING
Passing Parameter by Reference
Accessing Array element
Dynamic Memory Allocation :
Reducing size of parameter
Some other pointer applications :
--Passing Strings to function
--Provides effective way of implementing the different data
structures such as tree, graph, linked list
174

FILE HANDLING: GOALS
By the end of this unit we should understand …
 … how to open a file to write to it.
 … how to open a file to read from it.
 … how to open a file to append data to it.
 … how to read strings from a file.
 … how to write strings to a file.
175

DEFINITION
 A file is a collection of related data that a computers treats as a
single unit.
 Computers store files to secondary storage so that the contents
of files remain intact when a computer shuts down.
 When a computer reads a file, it copies the file from the storage
device to memory; when it writes to a file, it transfers data from
memory to the storage device.
176

OPERATIONS ON FILE
 Opening a file
 Reading data from a file
 Writing data to a file
 Closing a file
177

OPENING A FILE
 A file must be “opened” before it can be used.
FILE *fp;
:
fp = fopen (filename, mode);
 fp is declared as a pointer to the data type FILE.
 filename is a string - specifies the name of the file.
 fopen returns a pointer to the file which is used in all
subsequent file operations.
 mode is a string which specifies the purpose of opening the
file:
178

EXAMPLES
“r” :: open the file for reading only
“w” :: open the file for writing only
“a” :: open the file for appending data to it.
FILE *in, *out ;
in = fopen (“mydata.dat”, “r”) ;
out = fopen (“result.dat”, “w”);
FILE *empl ;
char filename[25];
scanf (“%s”, filename);
empl = fopen (filename, “r”) ;
179

CLOSING A FILE
 After all operations on a file have been completed, it must be closed.
 Ensures that all file data stored in memory buffers are properly written to
the file.
 General format: fclose (file_pointer) ;
FILE *xyz ;
xyz = fopen (“test”, “w”) ;
…….
fclose (xyz) ;
180

STANDARD C PREPROCESSORS
 The C preprocessor executes before a program is compiled.
 Some actions it performs are the inclusion of other files in the file being compiled,
definition of symbolic constants and macros, conditional compilation of program code
and conditional execution of preprocessor directives.
 Preprocessor directives begin with # and only white-space characters and comments may
appear before a preprocessor directive on a line.
 Macro definition
 #define, #undef
 File inclusion
 #include
 Conditional Compilation
 #if, #ifdef, #ifndef, #elseif, #else
181

#INCLUDE PREPROCESSOR DIRECTIVE
 The #include preprocessor directive has been used throughout
this text.
 The #include directive causes a copy of a specified file to
be included in place of the directive.
 The two forms of the #include directive are:
 #include <filename>
#include "filename"
 The difference between these is the location the preprocessor
begins searches for the file to be included.
 If the file name is enclosed in quotes, the preprocessor starts
searches in the same directory as the file being compiled for
the file to be included (and may search other locations, too).
182

#DEFINE PREPROCESSOR DIRECTIVE: SYMBOLIC CONSTANTS
 The #define directive creates symbolic constants—constants represented as symbols—
and macros—operations defined as symbols.
 The #define directive format is
 #define identifier replacement-text
 When this line appears in a file, all subsequent occurrences of identifier that do not
appear in string literals will be replaced by replacement-text automatically before the
program is compiled.
 Consider the following macro definition with one argument for the area of a circle:
 #define CIRCLE_AREA( x ) ( ( PI ) * ( x ) * ( x ) )
183

#ERROR AND #PRAGMA PREPROCESSOR DIRECTIVES:
 The #error directive
 #error tokens
prints an implementation-dependent message including the tokens
specified in the directive.
 The tokens are sequences of characters separated by spaces.
 For example,
 #error 1 - Out of range error
contains 6 tokens.
 When a #error directive is processed on some systems, the tokens in
the directive are displayed as an error message, preprocessing stops and
the program does not compile.
184

PREPROCESSOR DIRECTIVES
Directive Function
#define Defines a macro substitution
#undef Undefines a macro
#include Specifies the files to be included
#ifdef Test for a macro definition
#endif Specifies the end of #if
#ifndef Tests whether a macro is not defined
#if Test a compile time condition
#else Specifies alternatives when #if test fails
185

TYPES OF MACROS
 Macro substitution is a process where an identifier in a program is
replaced by a predefined string composed of one or more tokens.
 These directives can be divided into three categories:
 Macro substitution directives
 File inclusion directives
 Compiler control directives
186
Simple MS
Argumented MS
Nested MS

MACRO SUBSTITUTION
 General form:
#define identifier string
1. SIMPLE MS:
187
MACRO IDENTIFIER STRING
#define COUNT 200
#define FALSE 0
#define SUBJECTS 5
#define PI 3.1415
#define CAPITAL “LUCKNOW”

MACRO SUBSTITUTION
 2. Argumented MS
 The preprocessor permits us to define more complex & more useful
form of replacements.
 It takes the form:
#define identifier (f1, f2,………….fn) string
188
#define MAX(a, b) (((a)>(b))?(a):(b))
#define MIN (a, b) (((a)<(b))?(a):(b))
#define ABS(x) (((x)>(0))?(x):(-x))
#define STREQ(s1, s2) (strcmp((s1,)(s2))==0)
#define STRGT(s1, s2) (strcmp((s1,)(s2))>0)

MACRO SUBSTITUTION
 Nested MS:
We can also use one macro in the definition of another macro.
189
#define M 5
#define N M+1
#define SQUARE(x) ((x)* (x))
#define CUBE(x) (SQUARE (x) *(x))
#define SIXTH(x) (CUBE (x) * CUBE (x))

CONDITIONAL COMPILATION:
 Conditional compilation enables you to control the execution of preprocessor
directives and the compilation of program code.
 Each of the conditional preprocessor directives evaluates a constant integer
expression.
 Cast expressions, sizeof expressions and enumeration constants cannot be
evaluated in preprocessor directives.
 The conditional preprocessor construct is much like the if selection statement.
190

CONDITIONAL COMPILATION
 Structure similar to if
#if !defined( NULL )
#define NULL 0
#endif
 Every #if must end with #endif
 #ifdef short for #if defined( name )
 #ifndef short for #if !defined( name )
 Other statements
 #elif – equivalent of else if in an if structure
 #else – equivalent of else in an if structure
191

PASSING VALUES TO THE COMPILER
CALL BY VALUE CALL BY REFERENCE
Formal parameters are local variables
to callee.
Values of the actual parameters are
copied to the formal parameters when
function is called.
Conceptually simple.
Values of actual parameters are
protected.
Costly copying if parameters are large.
Can only return 1 value.
Formal parameters are pointers to
actual parameters.
Every use of the formal parameter is
implicitly dereferenced.
Actual parameters must have l-values.
(If not, either prohibit, or create
temporary unnamed variable in
caller).
Aliasing problem.
Can’t use in remote procedure call.
192

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