C语言 if...else语句
if语句后面可以跟随可选的else语句,该语句在布尔表达式为false时执行。
if…else - 语法
C编程语言中if.else语句语法为
if(boolean_expression) {
/* statement(s) will execute if the boolean expression is true */
} else {
/* statement(s) will execute if the boolean expression is false */
}
if…else - 流程图
if…else - 示例
#include <stdio.h>
int main () {
/* local variable definition */
int a=100;
/* check the boolean condition */
if( a < 20 ) {
/* if condition is true then print the following */
printf("a is less than 20\n" );
} else {
/* if condition is false then print the following */
printf("a is not less than 20\n" );
}
printf("value of a is : %d\n", a);
return 0;
}
编译并执行上述代码时,将生成以下结果-
a is not less than 20;
value of a is : 100
if…else if … else - 语法
If语句后面可以跟随可选的Else If.Else语句,这对于使用单个If.Else If语句测试各种条件非常有用。
C编程语言中if.else语句的语法是-
if(boolean_expression 1) {
/* Executes when the boolean expression 1 is true */
} else if( boolean_expression 2) {
/* Executes when the boolean expression 2 is true */
} else if( boolean_expression 3) {
/* Executes when the boolean expression 3 is true */
} else {
/* executes when the none of the above condition is true */
}
if…else if … else - 示例
#include <stdio.h>
int main () {
/* local variable definition */
int a=100;
/* check the boolean condition */
if( a == 10 ) {
/* if condition is true then print the following */
printf("Value of a is 10\n" );
} else if( a == 20 ) {
/* if else if condition is true */
printf("Value of a is 20\n" );
} else if( a == 30 ) {
/* if else if condition is true */
printf("Value of a is 30\n" );
} else {
/* if none of the conditions is true */
printf("None of the values is matching\n" );
}
printf("Exact value of a is: %d\n", a );
return 0;
}
编译并执行上述代码时,将生成以下结果:
None of the values is matching
Exact value of a is: 100