C Tutorial/Statement/If statement
Содержание
- 1 Checking for a Range of Values
- 2 if Comparisons and Their Opposites
- 3 if statement
- 4 if statement: compare the value from user input
- 5 if statement with two else statements
- 6 If with else statement
- 7 Operators Used in if Comparisons
- 8 The if-else-if statement
- 9 The if statement: a compound statement
- 10 To execute only one statement, opening and closing braces are not required
- 11 Use compound conditions to check for upper and lowercase letters
- 12 Use isdigit Function in if statement
- 13 Using nested ifs
Checking for a Range of Values
#include <stdio.h>
main()
{
int iResponse = 0;
printf("Enter a number from 1 to 10: ");
scanf("%d", &iResponse);
if ( iResponse < 1 || iResponse > 10 )
printf("\nNumber not in range\n");
else
printf("\nThank you\n");
}Enter a number from 1 to 10: 2
Thank you
if Comparisons and Their Opposites
if Comparison else Statement Executed By This Condition < >= == != > <= <= > >= < != ==
if statement
To conditionally execute statements, you can use the if or the if...else statement.
The general form of the if statement is
if(expr) {
s1 ;
s2 ;
....
}if statement: compare the value from user input
#include <stdio.h>
int main(void)
{
int number = 0;
printf("\nEnter an integer between 1 and 10: ");
scanf("%d",&number);
if (number > 5)
printf("You entered %d which is greater than 5\n", number);
if (number < 6)
printf("You entered %d which is less than 6\n", number);
return 0;
}Enter an integer between 1 and 10: 5
You entered 5 which is less than 6
if statement with two else statements
#include <stdio.h>
#include <stdlib.h>
int main()
{
char num[2];
int number;
printf("Enter a number from 0 to 9:");
gets(num);
number=atoi(num);
if(number<5)
{
printf("That number is less than 5!\n");
}
else if(number==5)
{
printf("You typed in 5!\n");
}
else
{
printf("That number is more than 5!\n");
}
return(0);
}Enter a number from 0 to 9:2
That number is less than 5!
If with else statement
The general format for an if-else statement is
if (condition)
simple or compound statement
else
simple or compound statement.Operators Used in if Comparisons
Comparison Meaning or Pronunciation "True" Example < Less than 1 < 5, 8 < 9 == Equal to 7 == 7, 1 == 1 > Greater than 7 > 5, 10 > 0 <= Less than or equal to 4 <= 5, 8 <= 8 >= Greater than or equal to 6 >= 5, 2 >= 2 != Not equal to 1 != 0, 1 != 3.99
The if-else-if statement
The general format for the if-else if statement is:
if (condition 1)
simple or compound statement
else if (condition 2)
simple or compound statement
else if ( condition 3)
simple or compound statement
.....
else if ( conditon n )
simple or compound statementThe if statement: a compound statement
If a compound statement is used, it must be enclosed in opening and closing braces.
#include<stdio.h>
main()
{
int i=5, j =1;
if (i > j){
i = i + 1;
printf("%d",i);
}
else
j = j +1;
}6
To execute only one statement, opening and closing braces are not required
#include <stdio.h>
main(){
int i = 5;
if(i > 0)
printf(" i > 0. \n");
}i > 0.
Use compound conditions to check for upper and lowercase letters
#include <stdio.h>
main(){
char cResponse = "\0";
printf("Enter the letter A: ");
scanf("%c", &cResponse);
if ( cResponse== "A" || cResponse == "a" )
printf("\nCorrect response\n");
else
printf("\nIncorrect response\n");
}Enter the letter A: 1
Incorrect response
Use isdigit Function in if statement
#include <stdio.h>
#include <ctype.h>
main()
{
char cResponse = "\0";
printf("\nPlease enter a letter: ");
scanf("%c", &cResponse);
if ( isdigit(cResponse)== 0 )
printf("\nThank you\n");
else
printf("\nYou did not enter a letter\n");
}Please enter a letter: 1
You did not enter a letter
Using nested ifs
#include <stdio.h>
#include <limits.h>
int main(void)
{
long test = 0L;
if( test % 2L == 0L) {
printf("The number %ld is even", test);
if ( (test/2L) % 2L == 0L)
{
printf("\nHalf of %ld is also even", test);
printf("\nThat"s interesting isn"t it?\n");
}
}
else
printf("The number %ld is odd\n", test);
return 0;
}The number 0 is even
Half of 0 is also even
That"s interesting isn"t it?
