C Program to Change String Case

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This C program is used to change string case with and without using strlwr and strupr functions.

Lowercase using strlwr function

Program:
#include <stdio.h>
#include <string.h>

int main()
{
    char string[] = "Strlwr in C";
    printf("%s\n",strlwr(string));
    return  0;
}

Uppercase using strupr function

Program:
#include <stdio.h>
#include <string.h>

int main()
{
    char string[] = "strupr in c";
    printf("%s\n",strupr(string));
    return  0;

}

Lowercase without strlwr function

Program:
#include <stdio.h>

void lower_string(char*);

int main()
{
    char string[100];
    
    printf("Enter a string to convert it into lower case\n");
    gets(string);
    
    lower_string(string);
    
    printf("Entered string in lower case is \"%s\"\n", string);
    
    return 0;
}

void lower_string(char *string)
{
    while(*string)
    {    
        if ( *string >= 'A' && *string <= 'Z' ) 
        {
        *string = *string + 32;
        }
        string++;    
    }
}

Uppercase without strupr function

Program:
#include <stdio.h>

void upper_string(char*);

int main()
{
    char string[100];
    
    printf("Enter a string to convert it into upper case\n");
    gets(string);
    
    upper_string(string);
    
    printf("Entered string in upper case is \"%s\"\n", string);
    
    return 0;
}

void upper_string(char *string)
{
    while(*string)
    {    
        if ( *string >= 'a' && *string <= 'z' )
        {
        *string = *string - 32;
        }
        string++;        
    }
}

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