Introduction to C Programming

1. Overview of Programming

2. Programming language
 The set of instruction written in a programming
language is called program.
 Two types:
1) Application Program: Program which direct the
computer to solve the problem of user.
eg. Word, excel, games etc
2) System Program: Program which direct the
computer to solve the problem of computer itself.
eg. OS, antivirus software etc

3.  To communicate with a computer it has to be instructed
to carry out various tasks like: what operations to
perform, how to present results, when and how to make
certain decisions and so on.
 These set of instructions have to be communicated to
the computer through a language called ‘programming
language’.
 Levels of programming language:
1)Machine language(low level)
2)Assembly language
3)Procedure oriented language(high level)
4)Fourth generation language(4GLs)
Programming language(Cont.)

4. Programming language(Cont.)

5. Programming language(Cont.)
1)Machine level language
 Computers are made of two-state electronic
components which can understand only pulse and no-
pulse (1 and 0) conditions.
 It consist of string of binary numbers(0 and 1).
 faster program execution
 It is very tedious to understand and remember the
various combinations of 1’s and 0’s representing data
and instructions.
 Every computer has its own machine language, the
programmer can not communicate with other computers
if he does not know its machine language.

6. 2)Assembly language
 It uses mnemonic codes such as ADD for addition, SUB
for subtraction etc.
 Memory locations containing data are given names
such as TOTAL, MARKS, TIME etc.
 Thus, instead of referring a location using its number, it
can be referred using the name given to it.
 A program written in assembly language must be
translated into machine language before it can be
executed. This translation is done by another program
called assembler.
Programming language(Cont.)

7.  Advantages of assembly language over machine
language:
 It saves programmer’s time.
 Fewer errors are made.
 They are easier to modify than machine language
programs.
Programming language(Cont.)

8. Programming language(Cont.)
3) Procedure oriented language (High level)
 This language consists of a set of words and symbols
and one can write programs using these in conjunction
with certain pre-specified rules of the language.
 A programming language such as C, FORTRAN,
or Pascal that enables a programmer to
write programs that are independent of a particular type
of computer.
 It is machine independent and a program written in high
level language can be run on different computers with
little or no modification.
 The main advantage of high-level languages over low-
level languages is that they are easier to read, write,
and maintain.

9.  Ultimately, programs written in a high-level language
must be translated into machine language by a
compiler or interpreter.
 faster program development
 It takes extra time for conversion and thus are less
efficient as compared to machine language programs.
Programming language(Cont.)

10. Programming language(Cont.)
4) Fourth generation language
 A non-procedural programming language that requires
less coding than lower-level languages.
 Eg. Command-line languages, database management
systems (DBMSs). Prolog, an artificial
intelligence language that applies rules to data to
arrive at solutions

11. Language translators
 Compiler: It checks the entire program and if error free,
produces a complete program in machine
language(object code).Then object code is loaded in
memory for execution.
 Interpreter: which analyzes and executes each line of
source code without looking at the entire program.

12. Compiler Interpreter
It checks whole program at
a stretch.
It checks program one by
one.
It throws all errors in a
program.
It throws errors of a single
line.
It is faster. It is slower.
It is less accurate. It is more accurate.
C, C++ uses it. Java uses it.
Language translators(Cont.)

13. Errors
 Types:
1)Syntax error:
• It occurs due to poor knowledge of programming
language.
• Eg. you may miss a semicolon or a curly bracket.
2) Logical error:
• it occurs due to poor knowledge of programming
technique.
• A logic error, or bug, is when your program compiles
and runs, but does the wrong thing.
• int average(int a, int b)
{
return a + b / 2; /* should be (a + b) / 2 */

14. Files generated by compiler
 Sample.c //source code
 Sample.obj //machine language
 Sample.bak //backup file
 Sample.exe //auto executable file

15. Q & A
1) A machine language program consist of instructions
written in..?
2) An Assembly language program consist of instructions
written in..?
 A)mnemonic
 B)0’s and 1’s
 C)Keywords
 D)English like words
3) Translator that translates the assembly language into
machine language is called..?
4) int a=10, b=0, c;
c=a/b; //syntax error or logical error?