C Programming - Basics of c -history of c

C Programming
By
Mrs. B. Dhivya M.C.A., M.Phil.,(Ph.D).,
Technical Trainer / Assistant Professor, Department of Computer Science,
Sri Ramakrishna College of Arts & Science, Coimbatore.
C Basics

Agenda
• What is C Language?
• History of C
• Features of C
• Structure of C Programs
• Tokens in C

What is C Language?
• C is a general-purpose, procedural, high-level
programming language.
• C language was developed by Dennis M. Ritchie at the
Bell Telephone Laboratories in 1972.
• It is a powerful and flexible language which was first
developed for the programming of the UNIX operating
System.
• C is one of the most widely used programming languages.
• C programming language is known for its simplicity and
efficiency.

EXAMPLE PROGRAM
#include <stdio.h>
#include<conio.h>
void main()
{
printf("Hiii, Studentsn");
getch();
}

Standard I/O
Standard Input :
printf() - This function stands for "print formatted" and is used for formatted
output. It allows you to specify the format of the output by using format
specifies like %d for integers, %f for floats, %s for strings, etc.
int num = 10;
printf("The number is: %dn", num);
Standard Output:
scanf() is a function in C programming used for taking input from the user. It
reads formatted data from the standard input (usually the keyboard) and
assigns the values to the variables passed as arguments.
scanf("%d", &num); // Reads an integer input from the user and stores it in
'num

Tokens in C
A token in C can be defined as the smallest individual element
of the C programming language that is meaningful to the
compiler. It is the basic component of a C program.

Keywords
The keywords are pre-defined or reserved words in a
programming language. Each keyword is meant to perform a
specific function in a program. C language
supports 32 keywords.
auto double int struct
break else long switch
case enum register typedef
char extern return union
const float short unsigned
continue for signed void
default goto sizeof volatile
do if static while

Identifiers
•Identifiers are used as the general terminology for the
naming of variables, functions, and arrays.
•These are user-defined names consisting of an arbitrarily
long sequence of letters and digits with either a letter or the
underscore(_) as a first character.
•Identifier names must differ in spelling and case from any
keywords.

Constants
The constants refer to the variables with fixed values. They are
like normal variables but with the difference that their values
can not be modified in the program once they are defined.
Constants may belong to any of the data types.
Examples of Constants in C
const int c_var = 20;
const int* const ptr = &c_var;

Strings
Strings are nothing but an array of characters ended with a null
character (‘0’). This null character indicates the end of the
string. Strings are always enclosed in double quotes. Whereas, a
character is enclosed in single quotes in C.
Examples of String
char str[20] = {‘g’, ’e’, ‘e’, ‘k’, ‘s’, ‘f’, ‘o’, ‘r’, ‘g’, ’e’, ‘e’, ‘k’,
‘s’, ‘0’};
char str[20] = “geeksforgeeks”;
Char s1[] = “geeksforgeeks”;

Special Symbols
Special symbols are used in C having some special
meaning and thus, cannot be used for some other purpose.
Brackets[]: Opening and closing brackets are used as array element references. These indicate
single and multidimensional subscripts.
Parentheses(): These special symbols are used to indicate function calls and function parameters.
Braces{}: These opening and ending curly braces mark the start and end of a block of code
containing more than one executable statement.
Comma (, ): It is used to separate more than one statement like for separating parameters in function
calls.
Colon(:): It is an operator that essentially invokes something called an initialization list.
Semicolon(;): It is known as a statement terminator. It indicates the end of one logical entity. That’s
why each individual statement must be ended with a semicolon.
Asterisk (*): It is used to create a pointer variable and for the multiplication of variables.
Assignment operator(=): It is used to assign values and for logical operation validation.
Pre-processor (#): The preprocessor is a macro processor that is used automatically by the compiler
to transform your program before actual compilation.
Period (.): Used to access members of a structure or union.
Tilde(~): Used as a destructor to free some space from memory.

Operators
Operators are symbols that trigger an action when applied to C variables and
other objects. The data items on which operators act are called operands.
Unary Operators: Those operators that require only a single operand to act
upon are known as unary operators. For Example increment and decrement
operators
Binary Operators: Those operators that require two operands to act upon
are called binary operators. Binary operators can further are classified into:
Arithmetic operators
Relational Operators
Logical Operators
Assignment Operators
Bitwise Operator
Ternary Operator: The operator that requires three operands to act upon is
called the ternary operator. Conditional Operator(?) is also called the ternary
operator.

Activity - 1
Program to Print an Integer
#include <stdio.h>
int main()
{
int number;
printf("Enter an integer: “, number); // reads and
stores input
scanf("%d", &number); // displays output
printf("You entered: %d", number);
return 0;
}

Output
Enter an integer:5
You entered:5

Activity - 2
Write a Program to Add Two Integers:.
#include <stdio.h>
int main() {
int num1, num2, sum;
printf("Enter two integers: “,num1, num2);
scanf("%d %d", &num1, &num2);
// calculate the sum
sum = num1 + num2;
printf("%d + %d = %d", num1, num2, sum);
return 0;
}

Output
Enter two integers: 12
11
12 + 11 = 23

Predict the Output or error of the C Program
1. void main()
{
int const * p=5;
printf("%d",++(*p));
}
Answer: Compiler error: Cannot modify a constant
value.
Explanation: p is a pointer to a "constant integer".
But we tried to change the value of the
"constant integer".

2. main()
{
printf("nab");
printf("bsi");
printf("rha");
}
Answer: hai
Explanation:
n (Newline): This escape sequence moves the cursor to the beginning of the
next line. When printf encounters n, it moves the cursor to the next line,
starting from the beginning.
b (Backspace): This escape sequence moves the cursor back one position
but doesn’t erase any character. When printf encounters b, it moves the
cursor back without clearing any character.
r (Carriage Return): This escape sequence moves the cursor to the
beginning of the current line without advancing to the next line. Any
characters printed after r overwrite the existing characters on that line.

3. #define clrscr() 100
main()
{
clrscr();
printf("%dn",clrscr());
}
Answer: 100
Explanation: Preprocessor executes as a seperate pass before the
execution of the compiler. So textual replacement of clrscr() to
100 occurs.

4. main()
{
printf("%p",main);
}
Answer: Some address will be printed.
Explanation: Function names are just addresses (just like
array names are addresses). main() is also a function. So the
address of function main will be printed. %p in printf
specifies that the argument is an address. They are printed
as hexadecimal numbers.

5. main()
{
clrscr();
}
clrscr();
Answer: No output/error
Explanation: The first clrscr() occurs inside a function.
So it becomes a function call. In the second clrscr(); is a
function declaration (because it is not inside any
function).

6. main()
{
int i=400,j=300;
printf("%d..%d");
}
Answer: 400..300
Explanation: printf takes the values of the first
two assignments of the program. Any number
of printf's may be given. All of them take only
the first two values. If more number of
assignments given in the program,then printf
will take garbage value

7. #include <stdio.h>
main()
{
int i=1,j=2;
switch(i)
{ case 1: printf("GOOD");
break;
case j: printf("BAD");
break;
}
}
Answer: Compiler Error: Constant expression required in
function main.
Explanation: The case statement can have only constant
expressions (this implies that we cannot use variable names
directly so an error).

Assessment 1
1. Program to check if the given character is a vowel or consonant .
2. C Program to Find the Largest Number Among Three Numbers

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