CODEWITHSUNDEEP
cloopswhile-loopchargetchar
Trabelsi Haythem
Trabelsi Haythem

Reputation: 1

C Language - WHILE loops working more that it's supposed to

I want to get the user to select a choice. So I declared a variable named Choice and I want it to input a char that can only be 'M', 'C', 'O' or 'P'.

This is my code :

char Choice;
printf("Select something to do  :\n'M':Model Parametering\n'C':Calendar creation\n'O':Calendar Output\n'P':Calendar Print\nChoice==>>");
    Choice = getchar();
    while(Choice!='M' && Choice != 'C' && Choice != 'O' && Choice != 'P'){
    printf("\nIncorrect choice, Try again\n");
    printf("Select something to do  :\n'P':Model Parametering\n'C':Calendar creation\n'O':Calendar Output\n'P':Calendar Print\nChoice==>>");
    Choice = getchar();}

The thing is when I test it with a wrong value (inputting a character that is NOT in ['M','C','O','P'], the while loop works more than once. For example if I input "TEST" instead of 'M', 'C', 'O' or 'P' the while works 5 times not only once like I want! Why is this happening?

Upvotes: 0

Views: 79

Answers (3)

user58697
user58697

Reputation: 7923

After entering TEST (4 character worth), you also pressed Enter. This is the fifth character (newline, really) passed to your program. Same way, after doing a single character (and Enter), the loop runs twice - first for the character itself, then for a newline.

Upvotes: 1

mahesh Rao
mahesh Rao

Reputation: 375

getchar() considers a character individually from stdin.By providing the input as "TEST", it first reads 'T' , loops again, reads E, loops again, reads S and so on, until it can ask for another character again, which is the 5th loop.

Upvotes: 0

Jeegar Patel
Jeegar Patel

Reputation: 27240

You have given input TEST it has 4 character so stdin has 4 character so 4 times getchar() can execute. then on next getchar() it will again wait for next input from stdin.

Upvotes: 0

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