Life Cycle of C Program, Structure of C Program, Keywords, Variables, Identifiers, Literals

1. PROGRAMMING IN C
Dr.K.Nithya
Assistant Professor,
Department of CSE,
SRMIST- Trichy

2. Life Cycle of C Program
IDE
Pre-processor
Compiler
Assembler
Loader
Linker
Program image
in memory
Source Code
add.c
Pre-processed
Code add.l
Assembly
Code add.s
Object Code
add.o
Executable Code
add.exe
Libraries &
Object files

3. Structure of C Program

4. Keywords
• In the C programming language, there are 32 keywords. All the 32 keywords have their meaning
which is already known to the compiler.
• Keywords are the reserved words with predefined meaning which already known to the compiler.

5. Keywords

6. Keywords

7. Identifiers
An identifier is a collection of characters which acts as the name of
variable, function, array, pointer, structure, etc.
Example
int marks;
char studentName[30];
Variable
Variable is a name given to a memory location where we can store different
values of the same datatype during the program execution.

8. Variable ( int number; )
A variable name may contain letters, digits and underscore symbol.
1.Variable name should not start with a digit.
2.Keywords should not be used as variable names.
3.A variable name should not contain any special symbols except underscore(_).
4.A variable name can be of any length but compiler considers only the first 31 characters
of the variable name.

9. Variable ( int number; )
The value of a variable can be changed, hence the name variable.
char ch = 'a';
// some code
ch = 'l’;
C is a strongly typed language. This means that the variable type cannot be
changed once it is declared.
int number = 5; // integer variable
number = 5.5; // error
double number; // error

10. Literals
Literals are data used for representing fixed values. They can be used
directly in the code.
For example: 1, 2.5, ‘c’ , ‘’ Good ‘’ , etc.``
• Integer Literals
• Floating-point Literals
• Character Literals
• String Literals

11. (i) Integer literal
It is a numeric literal that represents only integer type values. It represents the value neither in fractional nor
exponential part.
It can be specified in the following three ways:
● Decimal number (base 10)
It is defined by representing the digits between 0 to 9. For example, 45, 67, etc.
● Octal number (base 8)
It is defined as a number in which 0 is followed by digits such as 0,1,2,3,4,5,6,7. For example, 012, 034, 055, etc.
● Hexadecimal number (base 16)
It is defined as a number in which 0x or 0X is followed by the hexadecimal digits (i.e., digits from 0 to 9, alphabetical
characters from (a-z) or (A-Z)).

12. (ii) Floating point Literal
- Contains only floating-point values or real numbers.
- These real numbers contain the number of parts such as integer part, real part,
exponential part, and fractional part.
- The floating-point literal must be specified either in decimal or in exponential
form.
- Ex: 1.2, +9.0, -4.5 - Decimal Form
+1e23, -9e2, +2e-25 - Exponential Form

13. (iii) Character Literal
- Contains a single character enclosed within single quotes.
- If multiple characters are assigned to the variable, then, need to create a
character array.
- If we try to store more than one character in a variable, then the warning of a
multi-character character constant will be generated.

14. (iv) String Literal
- A string literal represents multiple characters enclosed within double-
quotes.
- It contains an additional character, i.e., '0' (null character), which
gets automatically inserted. This null character specifies the
termination of the string.

15. #include <stdio.h>
int main()
{
const int a=23; // constant integer
literal
printf("Integer literal : %d", a);
return 0;
}
Integer Literal
#include <stdio.h>
int main()
{
const float a=4.5; // constant float literal
const float b=5.6; // constant float literal
float sum;
sum=a+b;
printf("%f", sum);
return 0;
}
float literal

16. #include <stdio.h>
int main()
{
const char c='ak';
printf("%c",c);
return 0;
}
Character Literal
#include <stdio.h>
int main()
{
const char str[ ]= "Welcome n To n KEC";
printf("%s", str);
return 0;
}
String Literal

17. Escape Sequences
a Alarm or Beep
b Backspace
f Form Feed
n New Line
r Carriage Return
t Tab (Horizontal)
v Vertical Tab
Backslash
' Single Quote
" Double Quote
? Question Mark
nnn octal number
xhh hexadecimal number
0 Null

18. #include<stdio.h>
int main()
{
int number=50;
printf("Younarenlearningn'c' languagen"Do you know C language"");
return 0;
}
Example program for escape sequences