C Operators & I/O Functions
In this lesson we are going to discuss the following topics:
- ARITHMETIC OPERATORS
- UNARY OPERATORS
- RELATIONAL & LOGICAL OPERATORS
- ASSIGNMENT OPERATORS
- CONDITIONAL OPERATOR
- PRECEDENCE OF OPERATORS
- GETCHAR
- PUTCHAR
- SCANF
- PRINTF & ESCAPE SEQUENCE
- GETS
- PUTS
 |
| Learn C Program |
Let's see the brief information
There are 5 arithmetic operators in C. They are:
Operators Use
+ addition
- subtraction
* multiplication
/ division
% remainder after integer division (also known as modulus operator)
Example:
If integer variable x = 10 & y = 3
Expression Value
x + y 13
x - y 7
x * y 30
x / y 3
x % y 1
We are explaining some small program
Program-1
#include<stdio.h>
/* Example of Arithmetic Operators */
void main()
{ int a=2, b=3;
printf("a + b = %d\n",a+b);
printf("a - b = %d\n",a-b);
printf("a * b = %d\n",a*b);
printf("a / b = %d\n",a/b); }
Program-2
#include<stdio.h>
/* Example of Arithmetic Operators */
void main()
{ int a=6, b=12, c=6, avg=(a+b+c)/3;
printf("The Average of %d, %d, And %d Is : %d\n",a,b,c,avg);
}
Program-3
#include<stdio.h>
/* Example of find - Distance covered by a vehicle, if speed & time are given */
void main()
{ int speed=10, time=3, distance=speed*time;
printf("A Vehicle Travelling At %d KPH For %d Hours \n", speed, time);
printf("Will Cover %d Kilometeres, \n", distance); }
Program-4
#include<stdio.h>
/* Example of Priority of the Arithmetic Operators */
void main()
{ int a=5, b=10, c=15, ans=0;
ans = a+b/c;
printf("The Value Of Ans Is : %d\n",ans);
ans = b*c-a;
printf("The Value Of Ans Is : %d\n",ans);
ans = a*b/c;
printf("The Value Of Ans Is : %d\n",ans); ans = (a+b)*b/a;
printf("The Value Of Ans Is : %d\n",ans); }
Program-5
#include<stdio.h>
/* Example of Priority of the Arithmetic Operators */
void main()
{ int a, b=15, c=8, d=3, e=32 f=5;
a = a * c + e / d + f;
printf("The Value Of a = %d\n",a);
a = a * c + e / ( d + f);
printf("The Value Of a = %d\n",a);
a = a * (c + e) / d + f;
printf("The Value Of a = %d\n",a);
a = b * (c + e) / (d + f);
printf("The Value Of a = %d\n",a); }
Example: If floating-point variable x =12.5 & y =2.0
Expression Value
x + y 14.5
x - y 10.5
x * y 25.0
x / y 6.25
Example: If integer variable x =11 & y = -3
Expression Value
x + y 8
x - y 14
x * y -33
x / y -3
x % y 2
Example: If floating-point variable x = -0.66 & y = 4.50
Expression Value
x + y 3.84
x - y -5.16
x * y -2.97
x / y -0.146667
Example:
The algebraic formula The C arithmetic expression
a -[ ( b/ c) x d ] a - b / c * d
( a - b ) / (c x d ) ( a - b ) / (c * d ) i = 8, j = 15 & k = 4 w = 2 * ((i % 5) * (4 + (j-3) / (k+2)));
Evaluation:
w = 2 * ((8 % 5) * (4 + (15 - 3) / (4 + 2)))
w = 2 * (3 * (4 + (12/6)))
w = 2 * (3 * (4 + 2)) or u = i % 5;
w = 2 * (3 * 6) v = 4 + (j -3) / (k + 2);
w = 2 * 18 w = 2 (u * v);
w = 36
Unary Operators
There are 4 type of unary operators:
Operators use
- unary minus
++ increment operator
-- decrement operator
sizeof returns the size of operand
- A unary operators is that, which act upon a single operand to produce a new value.
- The 1st unary operator is unary minus, where a minus sign precedes a numerical constant, a variable or an expression.
- The unary minus operator is different from the arithmetic operator which denotes subtraction ( - ), and requires 2 separate operands.
-743 -0X7FFF -0.2 - (a + b)
- The 2nd unary operator is increment operator ++ , which causes its operand to be increased by one.
- The 3rd unary operator is decrement operator -- , which causes its operand to be decreased by one.
- The operand used with each of these operators must be a single variable.
Example: Expression Meaning New Value of i
if int i = 5; ++i i = i + 1 6
if int i = 5; ++i i = i + 1 4
- The increment and decrement operators can be utilized in 2 different ways, depending on whether the operator is written before or after the operand.
- If the operator precedes the operand ( e.g., ++i), then the operand will be altered in value before it is utilized for its intended purpose.
- If the operator follows the operands ( e.g., ++i), then the value of the operand will be altered after it is utilized.
Program-1
#include<stdio.h>
/* Example of increment, then display */
main()
{ int i =1;
printf("i = %d\n", i);
printf("i = %d\n", ++i);
printf("i = %d\n", i);
}
Program-2
#include<stdio.h>
/* Example of display, then increment */
main()
{ int i =1;
printf("i = %d\n", i);
printf("i = %d\n", ++i);
printf("i = %d\n", i);
}
The 4th unary operator is sizeof operator, which returns the size of its operand, in bytes.
Program-3
#include<stdio.h>
/* Example of sizeof() */
void main()
{ printf("The Size Of char = %d\n" , sizeof(char));
printf("The Size Of int = %d\n" , sizeof(int));
printf("The Size Of short = %d\n" , sizeof(short));
printf("The Size Of float = %d\n" , sizeof(float));
printf("The Size Of long = %d\n" , sizeof(long));
printf("The Size Of double = %d\n" , sizeof(double));
}
Program-4
#include<stdio.h>
/* Example of sizeof an array */
main()
{ char a1[ ] = "Computer";
printf("Number of characters = %d\n" , sizeof(a1));
}
Unary operators have a higher precedence than arithmetic operators.
Example:
int x = 10, y =20;
The value of - x + y will be - 10 + 20 = 10
But The value of -(x + y) will be -(10 + 20) = 30
Relational & Logical Operators
Operators Use
< less than
<= less than or equal to
> greater than
>= greater than or equal to
= = equal to
!= not equal to
&& and
|| or
! not
- These operators are used to form logical expressions representing conditions that are either true (int 1) or false (int 0)
int a = 1, b = 2, c=3;
Expression Meaning Value
a < b true 1
(a+b) >=c true 1
(a+b) >=c true 1
(b+c) > (a+5) false 0
c != 3 false 0
b = = 2 true 1
Example:
int i = 7;
float f = 5.5;
char c = 'w;
Expression Meaning Value
(i >= 6) && (c = = 'w') true 1
(i >= 6) || (c = = 119) false 0
(i < 11) && (i > 100) false 0
(c != 'p') || ((i + f) <= 10) true 1 Example:
int i = 7;
float f = 5.5;
Expression Meaning Value
f > 5 true 1
!(f > 5) false 0
i <=3 false 0
!(i <= 3) true 1 i > (f + 1) true 1
!(i > (f +1)) false 0 Assignment Operators
There are 6 assignment operators in C :
Operators use
= assign the value of an expression to an identifier
+= add and then assign
-= subtract and then assign
+= multiply and then assign
/= divide and then assign
%= evaluate remainder and then assign
Example:
int i ;
int j =5;
Expression Value
i = 3.3 3
i = 3.4 -3
i = j 5
i = j /2 2 i = 2 * (j / 2) 4
i = 'x' 120 i = '0' 48
Example:
Conditional Operator
int i ; i = j =5
int j ; Value 5 will be assigned to both i & j
Example :
int i = 5;
int j = 7;
float f = 5.5;
float g = -3.25;
Expression Meaning Value
i += 5 i = i + 5 10
f -= g f = f - g 8.75
j *= (i-3) j = j * (i-3) 14
f / =3 f = f / 3 1.833333
i %= (j -2) i = i % (j -2) 0
Program-1
#include<stdio.h>
/* Example on Assignment operator with after/before increment */
void main()
{ int a = 8, b=2, sum1;
int a = 8, b=2, sum1;
sum1= a+(++b); /* Increment Then Add */
printf("sum1 = %d\n" , sum1);
sum2=x+(y++); /* Add Then Increment */
printf("sum2 = %d\n", sum2);
}
- It can be used instead of if -else
- A conditional operator is written in the form:
expression1 ? expression2 : expression3
Evaluate:
If expression1 is true, expression2 is evaluated
If expression1 is false, expression3 is evaluated
Only one of the either expression2 or expression3 is evaluated when determining the value of a conditional expression.
Example:
flag = (i < 0) ? 0 : 100;
If the value of i is negative, then 0 will be assigned to flag
If the value of i is not negative, then 100 will be assigned to flag
Program-1
#include<stdio.h>
/* Example of ? : operator */
void main()
{ int num;
printf("\nEnter A Number :");
scanf( %d", &num);
sum2=x+(y++); /* Add Then Increment */
(num % 2) ? printf("\nYou Entered ODD"):printf("\nYou Entered EVEN");
} Precedence of Operators
Operator names Operator Evaluation
unary operators - ++ -- | sizeof R to L
arithmetic multiply, * / % L to R
divide & remainder
arithmetic add and + - L to R
subtract
relational operator < <= > .= L to R
equality operators = = | = L to R
logical and && L to R
logical or || L to R
conditional operator ? : R to L
assignment operator = += -= *= /+ %= R to L
Example:
int a, b, c;
c +=(a > 0 && a<=10) ? ++a : a/b;
Is evaluated as follows:
- if ( a > 0 && a<= 10) is true ++a is evaluated
- if ( a > 0 && a<= 10) is false a/b is evaluated
- the value of c is incremented (+=) by the value of conditional expression.
Program-1
#include<stdio.h>
/* Example of = =, !=, ? : , &&, and || */
void main()
{ int year;
printf("\nEnter A Year :");
scanf( %d", &year);
(year % 4 = = 0 && year % 100 !=0 || year % 400 = = 0)
? printf("\nLeap Year") : printf("\nNot A Leap Year");
} I/O Functions:
- An input/output function can be accessed from anywhere within a program simply by writing the function name, followed by a list of arguments enclosed in parentheses.
- The argument represent data items that are sent to the function.
- Some I/O functions do not require arguments, but parentheses must appear.
- Functions that return data items may appear within expression.
- Functions that do not return data items are separate statements.
- The hear file required by the standard I/O library functions is called stdio.h
- This file is entered into the program by an #include statement at the beginning of the program.
getchar( )
Purpose:
- Enter a single character from the standard input device.
- It returns a single character from a standard input device ( mainly a keyboard).
- This function does not require any arguments.
character variable = getchar ();
Program-1
#include<stdio.h>
/* Get a character from the user and display it back| */
void main()
{ char c;
c = getchar( );
printf("C contains : %s", c);
} Program-2
#include<stdio.h>
/* Get a character from the user and display it's ASCII Code */
void main()
{ char aski;
printf("\nEnter A Character : ");
aski = getchar( );
printf("\nThe ASCII Code For %s Is %d", aski,aski);
} Putchar
Purpose:
- Sends a single character to the standard output device
- It transmits a single character to a standard output device (mainly a Monitor)
- The character being transmitted, should be represented as a character-type variable.
- It must be expressed as an argument to the function.
Usage: putchar (character variable)
Program-1
#include<stdio.h>
/* Display a character */
void main()
{ putchar('A');
}
Program-2
#include<stdio.h>
/* Get a character from the user and display it back */
main()
{ char c;
c = getchar( );
putchar(c);
}
Program-2
#include<stdio.h>
/* Convert text to upper-case, and display */
main()
{ char text[80];
int counter, flag;
for(counter = 0; (text[counter] = getchar( )) ! = '\n'; ++counter);
flag = counter;
for(counter = 0; counter < flag; ++counter)
putchar(toupper(text[counter]));
}
- The 1st for statement creates a loop which causes the individual characters to be read into the computer and assigned to the array text[ ]
- The loop begins with a value of counter equal to zero.
- A character is then read into the computer from the standard input device and assigned to text[0]
- The value of counter is incremented.
- The process is repeated for the nest array elements till a newline character '\n' is encountered.
- The value of counter is assigned to flag.
- The 2nd 'for' displays the contents of text on the screen after converting them to upper-case.
scanf()
Purpose:
- Enter data items from the standard input device
- This function can be used to enter any combination of numerical values, singlecharacters and strings.
- The function returns the number of data items that have been entered.
Usage:
scanf(control string, arg1, arg2, .....,argn)
- control-string refers to a string containing certain required formating information.
- arg1, arg2,..., argn are arguments that represent the individual input data items.
Explanation:
- The control string comprises individual groups of characters, with one character group for each input data item.
- Each character group must begin with a percent sign ( % )
- A single character group will consist of the percent sign, followed by a conversion character which indicates the type of the corresponding data item.
- Table of conversion character for Data Input:
Conversion
Character Meaning
%c Single character
%d Decimal integer
%e Floating-point value
%f Floating-point value
%g Floating-point value
%h Short integer
%i Decimal, hexadeciamal or octal integer
%o Octal integer
%s String of character
%u Unsigned decimal integer
%x Hexadecimal integer
A prefix may precede certain conversion characters
Prefix Meaning
h short integer or short unsigned integer
l long integer, long unsigned integer or double
L long double
- Each variable name must be preceded by an ampersand (&)
- The arguments are actually pointers which indicate where the data items are stored in the computer's memory.
- array names should not begin with an ampersand.
Program-1
#include<stdio.h>
/* Example of scanf( ) using conversion character and ampersand character */
void main()
{ char text[20];
int partno;
float cost;
scanf("%s %d %f", text, &partno, &cost);
printf("The Value of text is : %s\n",text);
printf("The Value of partno is : %d\n",partno);
printf("The Value of partno is : %d\n",partno);
printf("The Value of cost is : %f\n",cost);
}
- FIELD means consecutive nonwhitespace characters that compose a data item collectively.
- The number of such character for a data item can be limited by specifying maximum field width.
- Unsigned integer indicating the field width should be placed between the percent sign ( % ) and the conversion character.
- The leftover character that extend beyond the specified field width will be ignored, or may be incorrectly interpreted as the components of the next data item.
Program-1
#include<stdio.h>
/* Example of scanf( ) with limited field width */
void main()
{ int a, b, c;
scanf("%3d, %3d, %3d, &a, &b, &c);
printf("a = %d \t b = %d \t c = %d \n", a,b,c);
}
Run 1:
User's Input : 1 2 3
Program's Output : a = 1 b = 2 c = 3
Run 2:
User's Input : 123 456 789
Program's Output : a = 123 b = 456 c = 789
Run 3:
User's Input : 123456789
Program's Output : a = 123 b = 456 c = 789
Run 4:
User's Input : 1234 5678 9
Program's Output : a = 123 b = 4 c = 567
printf( )
Purpose:
- Send data items to the standard output device.
- This function can be used to output any combination of numerical values, single characters and strings.
- This function moves data from the computer's memory to the standard output device.
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Learn how to write the Turbo C program step-by-step | Lesson -2
Reviewed by Neel Kamal
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October 31, 2020
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Reviewed by Neel Kamal
on
October 31, 2020
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