Basics of ‘C’

General Aspect of ‘C’

C was originally developed in the 1970s, by Dennis

Ritchie at Bell Telephone Laboratories, Inc.

C is a High level , general –purpose structured

programming language.

Instructions of C consists of terms that are very closely

same to algebraic expressions, consisting of certain
English keywords such as if, else, for ,do and while
• C contains certain additional features that
allows it to be used at a lower level , acting as
bridge between machine language and the
high level languages.
• This allows C to be used for system
programming as well as for applications
programming.
• So C is also called as “Middle Level Language”.
 Feature of ‘C’
• C is general purpose structured language.
• C is a programming language : It is simple to
implement and highly effective.
• C is a compatible language: It can run on all
machines right from 8088 to recent machines.
• C is a concise language: Only a small set of
instructions are required to get a task done.
• C has a rich built-in functions.
 Feature of ‘C’
• C provides a variety of data types, operators and
functions.
• C supports pointers which can directly access
the address of a variable in computer’s memory.
• C has only 32 keywords.
• C provides Modular Programming: It is a logical
collection of one or more functions are modules.
• C provides Dynamic Memory Allocation: This
allows to allocate memory during runtime.
• C is extensible: It continuously adds the library
functions supported by the C library.
• C is middle level language.
 System Ready

C Life Cycle Enter a C Source Code

( Filename.c) Edit the Source
Code
System Ready

Syntax
Error?
Yes

Link With System Library

Run the Executable Object

Code

Desired No
Result? Logical Errors?

Stop
 Structure of a ‘C’ Program
Documentation Section
// Program to add two numbers.
/* It tells purpose of C program.
Or we can use it for multiple lines comments.*/
Link section
#include<stdio.h>

Definition section
#define PI 3.1414
Global Declaration Section

Main() function Section

main()
{
Variable declaration / Initialization section;
Program Statements
}
Subprogram Section
Function 1()
{
Variable declaration / Initialization section;
Program Statements
}
 Sample of C Program
// This is my 1st program.
/* This program prints a Hello World on your output screen.*/
#include<stdio.h>
#include<conio.h>
void main()
{
clrscr();
printf(“Hello World”);
getch();
}
C program to print your Name, Department and
College Name on screen.
#include<stdio.h>
#include<conio.h>
void main()
{
clrscr();
printf(“Vishal Patel”);
printf(“\n Department : Computer Engineering”);
printf(“\n SVMIT - Bharuch”);
getch();
}
 The Character set of ‘C’
C language consist of some characters set, numbers and some special
symbols. The character set of C consist of all the alphabets of English
language.
C consist of
Alphabets a to z, A to Z
Numeric 0,1 to 9
Special Symbols {,},[,],?,+,-,*,/,%,!,;,and more
The words formed from the character set are building blocks of C and are
sometimes known as tokens. These tokens represent the individual entity of
language.
The following different types of token are used in C
1) Identifiers 2)Keywords 3)Constants
4) Operators 5)Punctuation Symbols
 Identifiers

• A 'C' program consist of two types of elements , user

defined and system defined. Identifiers is nothing but a
name given to these elements.
• An identifier is a word used by a programmer to name a
variable , function, or label.
• identifiers consist of letters and digits, in any order, except
that the first character or label.
• Identifiers consist of letters and digits if any order, except
that the first character must be letter.
• Both Upper and lowercase letters can be used
 Keywords
• Keywords are nothing but system
auto double int struct
defined identifiers.
• Keywords are reserved words of break else long switch
the language.
• They have specific meaning in the case enum register typedef
language and cannot be used by
the programmer as variable or char extern return union
constant names
const float short unsigned
• C is case sensitive, it means these
must be used as it is
continue for signed void
• 32 Keywords in C Programming
default goto sizeof volatile

do if static while
 Variables
• A variable is nothing but a name given to a storage area that our
programs can manipulate.

• Each variable in C has a specific type, which determines the size

and layout of the variable's memory; the range of values that can
be stored within that memory; and the set of operations that can
be applied to the variable.

• The name of a variable can be composed of letters, digits, and the

underscore character. It must begin with either a letter or an
underscore. Upper and lowercase letters are distinct because C is
case-sensitive.
 Variables

• There are following basic variable types −

Type Description
char Typically a single octet(one byte). This is an integer type.
int The most natural size of integer for the machine.
float A single-precision floating point value.
double A double-precision floating point value.
void Represents the absence of type.
 Constants
• A constant is a value or an identifier whose value cannot be
altered in a program. For example: 1, 2.5,
• As mentioned, an identifier also can be defined as a constant.
eg. const double PI = 3.14
• Here, PI is a constant. Basically what it means is that, PI and
3.14 is same for this program.

Integer constants
• A integer constant is a numeric constant (associated with
number) without any fractional or exponential part. There are
three types of integer constants in C programming:
• decimal constant(base 10)
• octal constant(base 8)
• hexadecimal constant(base 16)
 Constants

Floating-point constants
• A floating point constant is a numeric constant that has either
a fractional form or an exponent form. For example:
2.0,0.0000234,-0.22E-5

Character constants
• A character constant is a constant which uses single quotation
around characters. For example: 'a', 'l', 'm', 'F'

String constants
• String constants are the constants which are enclosed in a
pair of double-quote marks. For example: "good" ,"x","Earth
is round\n"
 Escape Sequences
Sometimes, it is necessary to use characters which cannot be typed or has special
meaning in C programming. For example: newline(enter), tab, question mark etc.
In order to use these characters, escape sequence is used.
• For example: \n is used for newline. The backslash ( \ ) causes "escape" from the
normal way the characters are interpreted by the compiler.Escape
Sequences Character
• \b Backspace
• \f Form feed
• \n Newline
• \r Return
• \t Horizontal tab
• \v Vertical tab
• \\ Backslash
• \' Single quotation mark
• \" Double quotation mark
• \? Question mark
• \0 Null character
 Operators in C:An operator is a symbol which operates on a value or a
variable. For example: + is an operator to perform addition.

C programming has wide range of operators to perform various

operations. For better understanding of operators, these
operators can be classified as:
• Arithmetic Operators
• Increment and Decrement Operators
• Assignment Operators
• Relational Operators
• Logical Operators
• Conditional Operators
• Bitwise Operators
• Special Operators
 Arithmetic Operator

• Operator Meaning of Operator

• + addition or unary plus
• - subtraction or unary minus
• * multiplication
• / division
• % remainder after
division( modulo division)
 Increment and Decrement Operators

1. C programming has two operators increment ++

and decrement -- to change the value of an operand
(constant or variable) by 1.
2. Increment ++ increases the value by 1 whereas
decrement -- decreases the value by 1.
3. These two operators are unary operators, meaning
they only operate on a single operand.
eg. int a=10, b=100
++a = 11
--b = 99
 C Assignment Operators

• An assignment operator is used for assigning a value

to a variable. The most common assignment
operator is =
• Operator Example Same as
• = a=b a=b
• += a += b a = a+b
• -= a -= b a = a-b
• *= a *= b a = a*b
• /= a /= b a = a/b
• %= a %= b a = a%b
 C Relational Operators
• A relational operator checks the relationship between two
operands. If the relation is true, it returns 1; if the relation is
false, it returns value 0.
• Relational operators are used in decision making and loops.
Operator Meaning of Operator Example
• == Equal to 5 == 3 returns 0
• > Greater than 5 > 3 returns 1
• < Less than 5 < 3 returns 0
• != Not equal to 5 != 3 returns 1
• >= Greater than or equal to 5 >= 3 returns 1
• <= Less than or equal to 5 <= 3 return 0