C Program to Convert Lowercase Characters by Uppercase and Vice-Versa

This is a C program to replace lowercase characters by uppercase & vice-versa.

Problem Description

This program accepts the sentence and replaces lowercase characters by uppercase & vice-versa.

Problem Solution

1. Take the sentence as input.
2. Using (islower()? toupper():tolower()) function replace lowercase characters by uppercase & vice-versa.
3. Print the output and exit.

Program/Source Code

Here is source code of the C program to replace lowercase characters by uppercase & vice-versa. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

```
/*
```

 * C program to read an English sentence and replace

 * lowercase characters by uppercase and vice-versa.

 * Output the given sentence as well as the converted

```
 * sentence on two different lines.
```
```
 */
```
```
#include <stdio.h>
```
```
#include <ctype.h>
```
```
 
```
```
void main()
```
```
{
```
```
    char sentence[100];
```
```
    int count, ch, i;
```
```
 
```
```
    printf("Enter a sentence \n");
```

    for (i = 0;(sentence[i] = getchar()) != '\n'; i++)

```
    {
```
```
        ;
```
```
    }
```
```
    sentence[i] = '\0';
```

    /*  shows the number of chars accepted in a sentence */

```
    count = i;
```

    printf("The given sentence is   : %s", sentence);

    printf("\n Case changed sentence is: ");

```
    for (i = 0; i < count; i++)
```
```
    {
```

        ch = islower(sentence[i])? toupper(sentence[i]) :

```
tolower(sentence[i]);
```
```
        putchar(ch);
```
```
    }
```
```
}
```

Program Explanation

1. Take an an English sentence as input and store it in the array sentence[].
2. Copy the last letter’s position in the array to the variable count.
3. Using for loop and (islower()? toupper():tolower()) function replace lowercase characters by uppercase & vice-versa. Store this in the variable ch.
4. Print the variable ch as output and exit.

Runtime Test Cases

Enter a sentence
wELCOME tO sANFOUNDRY
The given sentence is   : wELCOME tO sANFOUNDRY
Case changed sentence is: Welcome To Sanfoundry

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If you wish to look at other example programs on Strings, go to C Programming Examples on Strings. If you wish to look at programming examples on all topics, go to C Programming Examples.

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