This document provides an introduction to the C programming language. It discusses what a programming language and computer program are, and defines key concepts like algorithms, flowcharts, variables, data types, constants, keywords, and instructions. It also outlines the basic structure of a C program, including header files, functions, comments, and compilation/execution. The document explains the different character sets and components used to write C programs, such as variables, arithmetic operations, and control structures.

1. Mrs. Komal R. Pardeshi
Assisttant Professor,
Computer Science & Engg. Dept
Walchand Institute of Technology
Solapur, Maharashtra, India

2. Chapter 1
Introduction to C
What is Programming Language?
 A programming language is a set of commands, instructions, and other syntax use to create a
software program.
What is Program ?
 A computer program is a collection of instructions that performs a specific task when
executed by a computer.
 A computer program is usually written by a computer programmer in a programming
language.
What is an algorithm?
 Algorithm is step by step procedure to solve a given problem.
 Algorithm can perform calculation , data processing.
 It is a first step before writing any Computer program
What is Flowchart?
 Flowchart is pictorial representation of algorithm.
 flowchart symbols represent the various actions of a computer program
Start/ End
Process
Decision
Input / Output
Display Result

3. Getting Started With C
 Steps in Learning English
To learn english or any mother toungue language we need to learn first Alphates , then using
alphabets we form words , using words we form sentences and using centences we form
paragraph.
 Steps in Learning 'C' Language
Similarly, to learn any Computer language we need to understand Characeter set required for that
language , using this character set it forms constants, keywords, and variables. Using these
instruction is formed and set of instruction is nothing but a program.
'C' character Set
'C' contains total 256 characters. Every C character has American Standard Code
for Information Interchage (ASCII) Values.The characters in C are grouped into the following two
categories:
1. Source character set
a. Alphabets
b. Digits
c. Special Characters
d. White Spaces
2. Execution character set
a. Escape Sequence
Alphabets Words Sentences Paragraphs
' C ' character Set
Instruction
Set of
Instructions
Program
Constanats
,Variable,Keyword

4. 1. Source character set
a. ALPHABETS
Uppercase letters : A-Z (Ascii value : 65 to 90)
Lowercase letters : a-z (Ascii value : 97 to 122)
b. DIGITS
0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ( Ascii value : 48 to 57)
c. SPECIAL CHARACTERS
~ tilde , % percent sign , | vertical bar , @ at symbol , + plus sign, < less than,
_ underscore, - minus sign , > greater than , ^ caret , # number sign , = equal to,
& ampersand , $ dollar sign , / slash , ( left parenthesis , * asterisk , back slash
) right parenthesis , ′ apostrophe , : colon , [ , left bracket , " quotation mark , ; semicolon
] right bracket , ! exclamation mark , , comma , { left flower brace , ? Question mark , . dot
operator , } right flower brace
d. WHITESPACE CHARACTERS
b blank space , t horizontal tab , v vertical tab , r carriage return , f form feed , n new line
Back slash , ’ Single quote , " Double quote , ? Question mark , 0 Null, a Alarm (bell)
2. Execution character set
Certain ASCII characters are not displayed on the screen or printer. Examples are backspacing,
moving to a newline, or ringing a bell.
They are used in output statements. Escape sequence usually consists of a backslash and a letter or a
combination of digits. An escape sequence is considered as a single character but a valid character
constant.
These are employed at the time of execution of the program. Execution characters set are always
represented by a backslash () followed by a character. Note that each one of character constants
represents one character, although they consist of two characters. These characters combinations are
called as escape sequence.
All white space characters given above are execution characters.
• 'C' Constants C Constanats
Primary Constants Secondary Constanats

5. • Primary Constants :
i) Integer Constants
ii) Real (float) Constants
iii) Character Constants
i) Intger Constants :
An integer constant is a numeric constant (associated with number) without any
fractional or exponential part.
Rules for Constructing Integer Constant :
1) An integer constant must have at least one digit.
2) It must not have a decimal point.
3) It can either be positive or negative.
4) No commas or blanks are allowed within an integer constant.
5) If no sign precedes an integer constant, it is assumed to be positive.
6) The allowable range for integer constants is -32768 to 32767
Actually, the range of the integer constant depends on the compiler. The above mentioned
range is for 16-bit compiler. However, for a 32-bit compiler the range would be even greater.
Decimal Integer constant:
• 0 to 9
• E.g.: 49, 58, -62 … (40000 cannot come because it is > 32767)
Octal Integer constant:
• 0 to 7
• Add “0” before the value.
• E.g.: 045, 056, 067
Hexadecimal Integer constant:
• 0 to 9 and A to F
• Add 0x before the value
• E.g.: 0x42, 0x56, 0x67
ii) Real (Float)Constant : An integer constant is a numeric constant (associated with number) with
fractional or exponential part.
Rules for constructing Real constants (Fractional Form)
1) A real constant must have at least one digit
2) It must have a decimal point
3) It could be either positive or negative
4) If no sign precedes an integer constant, it is assumed to be positive.
5) No commas or blanks are allowed within a real constant.
E.g.: +867.9, -26.9876, 654.0

6. Rules for constructing Real constants (Exponential Form)
1) The mantissa part and the exponential part should be separated by the letter ‘e’
2) The mantissa may have a positive or negative sign(default sign is positive)
3) The exponent must have at least one digit
4) The exponent must be a positive or negative integer(default sign is positive)
5) The range of real constants in exponential form is -3.4e38 and +3.4e38
E.g.: +3.2e-4, 4.1e8, -0.2e+4, -3.2e-4
iii) Character Constant :
Rules for constructing Character constant
1) A character constant is an alphabet, a single digit or a single special symbol enclosed
within inverted commas. Both the inverted commas should point to the left. For example, ’S’
is a valid character constant whereas ‘S’ is not.
2) The maximum length of a character constant can be 1 character. Allots 1 byte of memory
E.g.: ’B’, ’l’, ’#’
• Secondary Constants : Array , Structure , union
• 'C' variables
• A variable is an entity whose value keeps on changing throughout the program execution.
• As we all know, data is stored in the memory of the computer.
• Actually, data is not stored in the variable. , rather a variable is the name given to the
memory location.
• A variable name is an entity that points to a particular memory location.
• Variable can be of different types.
Rules for constructing variable names
1. A Variable name consists of any combination of alphabets, digits and underscores. Some
compiler allows variable names whole length could be up to 247 characters. Still it would be
safer to stick to the rule of 31 characters. Please avoid creating long variable name as it adds
to your typing effort
2. The first character of the variable name must either be alphabet or underscore. It should not
start with the digit.
3. No commas and blanks are allowed in the variable name
4. No special symbols other than underscore are allowed in the variable name

7. Note : We cannot Use Keywords for – For Declaring Variable Name, For
Function Name and for declaring Constant Variable
We need to declare the type of the variable name before making use of that name in the
program. Type declaration can be done as follows:
To declare a variable as integer, follow the below syntax:
int variable_name;
Here int is the type of the variable named variable_name. ‘int’ denotes integer type.
'C' Keywords
• Keywords are those words whose meaning is already defined by Compiler
• Cannot be used as Variable Name
• There are 32 Keywords in C
• C Keywords are also called as Reserved words .
auto double int struct
break else long switch
case enume register typedef
char extern return union
const float short unsigned
continue for signed void
default goto sizeof volatile
do if static while
'C' Instructions
There are three types of instructions in C. They are as follows:
1) Type Declaration Instruction
2) Arithmetic Instruction
3) Control instruction
1) Type Declaration instruction :
• It is used to declare the type of variables used in C.
• Any variable we want to use in the program must be declared before using it.
• This declaration is done using Type declaration instruction.
• This declaration is done at the beginning of the main() function.
• e.g int num;

8. 2) Arthmetic Instruction :
• Arithmetic instructions are used to perform arithmetic operations on variables and
constants.
• These are operands and operators.
• The variables and constants on which arithmetic operation is done by arithmetic
operators are called operands.
• e.g int a = 5, b = 10, c;
c = a + b;
Here, ( a,b,c ) are operands and (= , + ) are operators.
Similarly, a= a+1 ;
Here (a , 1 ) are operands and (= , + ) are operators.
3) Control Instructions
• Control instruction is used to control the sequence (flow) of the program.
• if, if..else, for, while , do... while , switch are used for decision
control statements
Structure of C Program
// structure of C program
// declaration of header files
#include<stdio.h>
#include<conio.h>
main() // function main
{
declartion of variables;
clrscr(); //clear screen
set of Instructions ;
getch(); //remain on o/p screen till user enters character
} // end of main
Note : Comments are the lines which are written by programmer for own
understanding . These are the lines which are not recognised by C compiler while
compiling the program.
In C single line comment is given by // and multiline comment is given by /*.....*/
Note : Use Turboc editor to write , compile and execute C program on Windows OS. To
save C program use .c extension. F9 to compile and ctr+F9 to Run . On Linux OS
write program using available editor(gedit,eclipse etc) compile using cmd cc filename.c
and after successful compilation execute using ./a.out