Programming Forums > Application Development > C++

hipolito · Feb 17th, 2005, 8:09 AM

hello all,

I am doing a little programming on C and I need a little help.
User can enter in a field a number (code) or letter (name), how do find out if the variable he typed in was letter or number???

Thank you all.

Infinite Recursion · Feb 17th, 2005, 8:51 AM

#include <ctype.h>

isdigit() - tests if character is a digit
isalpha() - tests for alphabetic character

hipolito · Feb 17th, 2005, 9:58 AM

Well, thx a lot, it was realy what I was looking for, but still I got an error when I enter a number... segmentation error...

This is what I have:

printf("\nType number or name: ");
scanf("%d", value);
if (isdigit(value))
printf("\nNumber");
else
printf("\nLetter");

What should I do?

Thx again.

Hockeyman · Feb 17th, 2005, 10:40 AM

The scanf function uses pointers (aaaaaarrrgggghhhh)

try:

(Toggle Plain Text)

printf("\nType number or name: ");
scanf("%d", &value);
if (isdigit(value))
printf("\nNumber");
else
printf("\nLetter");

I'm not sure if this'll make any difference, but I'd use %c in the scanf to read in a char, instead of %d to read in a decimal integer - although that could just be my preference rather than any C rule.

hipolito · Feb 17th, 2005, 11:01 AM

Nope, I tryed both with "&" and "%c", none works....

Hockeyman · Feb 17th, 2005, 11:10 AM

how did you declare your variable "value"?

Another thing I've just noticed - you have in your printf for the user to enter a number or a name - but your scanf isn't set up to read strings. If they enter a full name, it'll just read the first character and leave the rest in the input buffer. You can fix it by asking the user to enter a number or a letter (easiest), or declaring value as a string and using %s in scanf to read (trickier).

hipolito · Feb 17th, 2005, 11:19 AM

I have tryed both int value and char value.....

I think the problem is scanf, it might not accept letter as input.

oh my god, would that be it???

I also tryed the atoi(value)...still shiiitous...

Hockeyman · Feb 17th, 2005, 1:11 PM

scanf will accept anything that is typed as input...might not interpret it like you think it's going to though.

Assuming you've included the correct libraries etc, that code should work.
There may be a problem somewhere else in your code.

In an earlier post you said it wasn't accepting numbers, your last post said letters - which isn't it accepting? What exactly is the error message you're getting? Does it compile and give a run-time error, or will it not even compile?

Infinite Recursion · Feb 17th, 2005, 1:41 PM

Here ya go... thnx for showing effort.

(Toggle Plain Text)

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>

int main (void)
{
char value;
    
printf("\nType number or name: ");
scanf("%d", &value);

if (isalpha(value))
{
    printf("\nLetter");
}
else 
{
    printf("\nNumber");
}

system("PAUSE");
return 0;
}

hipolito · Feb 18th, 2005, 3:59 AM

This is what I did:

void routine()
char value;
printf("\nEnter a value: ");
scanf("%d", &value);
if (isalpha(ponto))
printf("\nLetter");
else
printf("\nNumber");
os_exit(0);

Just what Infinite did, well even letter or a number shows Number on my screen... I guess difining it as char, whaever I type will aways be a string...

and Hockeyman, the program compiles just well, and the error shown is when I define the value as int and type a letter... so I must use the "%d" on scanf to get it work for both letters and number, but still the if clause will always go on ELSE option...

Feb 17th, 2005, 8:09 AM	#1
hipolito Programmer Join Date: Feb 2005 Posts: 41 Rep Power: 0	number or letter??? hello all, I am doing a little programming on C and I need a little help. User can enter in a field a number (code) or letter (name), how do find out if the variable he typed in was letter or number??? Thank you all.

Feb 17th, 2005, 8:51 AM	#2
Infinite Recursion Programming Guru Join Date: Jul 2004 Location: United States Posts: 3,467 Rep Power: 8	#include <ctype.h> isdigit() - tests if character is a digit isalpha() - tests for alphabetic character __________________ http://jasonpowers.net "There are a thousand hacking at the branches of evil to one who is striking at the root."

Feb 17th, 2005, 9:58 AM	#3
hipolito Programmer Join Date: Feb 2005 Posts: 41 Rep Power: 0	thx, but..... Well, thx a lot, it was realy what I was looking for, but still I got an error when I enter a number... segmentation error... This is what I have: printf("\nType number or name: "); scanf("%d", value); if (isdigit(value)) printf("\nNumber"); else printf("\nLetter"); What should I do? Thx again.

Feb 17th, 2005, 10:40 AM	#4
Hockeyman Programmer Join Date: Jan 2005 Location: Vancouver, Canada Posts: 60 Rep Power: 4	The scanf function uses pointers (aaaaaarrrgggghhhh) try: (Toggle Plain Text) printf("\nType number or name: "); scanf("%d", &value); if (isdigit(value)) printf("\nNumber"); else printf("\nLetter"); printf("\nType number or name: "); scanf("%d", &value); if (isdigit(value)) printf("\nNumber"); else printf("\nLetter"); I'm not sure if this'll make any difference, but I'd use %c in the scanf to read in a char, instead of %d to read in a decimal integer - although that could just be my preference rather than any C rule. __________________ ~ You know, Hobbes, some days even my lucky rocketship underpants don't help. ~ read my blog @ My Lucky Rocketship Underpants

Feb 17th, 2005, 11:01 AM	#5
hipolito Programmer Join Date: Feb 2005 Posts: 41 Rep Power: 0	nope Nope, I tryed both with "&" and "%c", none works....

Feb 17th, 2005, 11:10 AM	#6
Hockeyman Programmer Join Date: Jan 2005 Location: Vancouver, Canada Posts: 60 Rep Power: 4	how did you declare your variable "value"? Another thing I've just noticed - you have in your printf for the user to enter a number or a name - but your scanf isn't set up to read strings. If they enter a full name, it'll just read the first character and leave the rest in the input buffer. You can fix it by asking the user to enter a number or a letter (easiest), or declaring value as a string and using %s in scanf to read (trickier). __________________ ~ You know, Hobbes, some days even my lucky rocketship underpants don't help. ~ read my blog @ My Lucky Rocketship Underpants Last edited by Hockeyman; Feb 17th, 2005 at 11:18 AM.

Feb 17th, 2005, 11:19 AM	#7
hipolito Programmer Join Date: Feb 2005 Posts: 41 Rep Power: 0	oh oh I have tryed both int value and char value..... I think the problem is scanf, it might not accept letter as input. oh my god, would that be it??? I also tryed the atoi(value)...still shiiitous...

Feb 17th, 2005, 1:11 PM	#8
Hockeyman Programmer Join Date: Jan 2005 Location: Vancouver, Canada Posts: 60 Rep Power: 4	scanf will accept anything that is typed as input...might not interpret it like you think it's going to though. Assuming you've included the correct libraries etc, that code should work. There may be a problem somewhere else in your code. In an earlier post you said it wasn't accepting numbers, your last post said letters - which isn't it accepting? What exactly is the error message you're getting? Does it compile and give a run-time error, or will it not even compile? __________________ ~ You know, Hobbes, some days even my lucky rocketship underpants don't help. ~ read my blog @ My Lucky Rocketship Underpants

Feb 17th, 2005, 1:41 PM	#9
Infinite Recursion Programming Guru Join Date: Jul 2004 Location: United States Posts: 3,467 Rep Power: 8	Here ya go... thnx for showing effort. (Toggle Plain Text) #include <stdio.h> #include <ctype.h> #include <stdlib.h> int main (void) { char value; printf("\nType number or name: "); scanf("%d", &value); if (isalpha(value)) { printf("\nLetter"); } else { printf("\nNumber"); } system("PAUSE"); return 0; } #include <stdio.h> #include <ctype.h> #include <stdlib.h> int main (void) { char value; printf("\nType number or name: "); scanf("%d", &value); if (isalpha(value)) { printf("\nLetter"); } else { printf("\nNumber"); } system("PAUSE"); return 0; } __________________ http://jasonpowers.net "There are a thousand hacking at the branches of evil to one who is striking at the root."

Feb 18th, 2005, 3:59 AM	#10
hipolito Programmer Join Date: Feb 2005 Posts: 41 Rep Power: 0	Well here it goes! This is what I did: void routine() char value; printf("\nEnter a value: "); scanf("%d", &value); if (isalpha(ponto)) printf("\nLetter"); else printf("\nNumber"); os_exit(0); Just what Infinite did, well even letter or a number shows Number on my screen... I guess difining it as char, whaever I type will aways be a string... and Hockeyman, the program compiles just well, and the error shown is when I define the value as int and type a letter... so I must use the "%d" on scanf to get it work for both letters and number, but still the if clause will always go on ELSE option...

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Programming Forums > Application Development > C++

number or letter???