Switch Problem

This is a discussion on Switch Problem within the C Programming forums, part of the General Programming Boards category; Code: #include <stdio.h> char option; void PURCHASE(), VIEW(), QUIT(); void BUSINESS(), ECONOMY(); void main(){ printf("AIRLINE RESERVATION SYSTEM \n"); printf("P - ...

  1. #1
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    Switch Problem

    Code:
    #include <stdio.h>
    
    char option;
    
    void PURCHASE(), VIEW(), QUIT();
    void BUSINESS(), ECONOMY();
    
    void main(){
    	printf("AIRLINE RESERVATION SYSTEM \n");
    	printf("P - to Purchase Ticket \n");
    	printf("V - to View Arrangement \n");
    	printf("Q - to Quit the system \n");
    	printf("Enter the option : ");
    	scanf_s("%c", &option);
    	getchar();
    
    	switch(option){
    		case '1':
    		case 'P':
    		case 'p':
    			printf("Purchase\n");
    			//PURCHASE();
    			break;
    
    		case '2':
    		case 'V':
    		case 'v':
    			printf("View\n");
    			//VIEW();
    			break;
    
    		case '3':
    		case 'Q':
    		case 'q':
    			printf("Quit\n");
    			//QUIT();
    			break;
    
    		default:
    			printf("Invalid Option \n");
    			break;
    	}
    }
    Please help me see what is the problem, no matter that character or number I entered, the program also display Invalid Option.

  2. #2
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    Most likely because the next scanf reads a newline, and thus ends up in the "invalid option", as you do not have any entry for '\n'. You could verify this by adding a '\n' case in your switch, and print a message "got a newline" or some such.

    To fix that, add a space in the format string, " %c" to read out any "whitespace" characters (newline belongs to this category).

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  3. #3
    DESTINY BEN10's Avatar
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    Quote Originally Posted by ahhak1989 View Post
    Code:
    #include <stdio.h>
    
    char option;
    
    void PURCHASE(), VIEW(), QUIT();
    void BUSINESS(), ECONOMY();
    
    void main(){
    	printf("AIRLINE RESERVATION SYSTEM \n");
    	printf("P - to Purchase Ticket \n");
    	printf("V - to View Arrangement \n");
    	printf("Q - to Quit the system \n");
    	printf("Enter the option : ");
    	scanf_s("%c", &option);
    	getchar();
    
    	switch(option){
    		case '1':
    		case 'P':
    		case 'p':
    			printf("Purchase\n");
    			//PURCHASE();
    			break;
    
    		case '2':
    		case 'V':
    		case 'v':
    			printf("View\n");
    			//VIEW();
    			break;
    
    		case '3':
    		case 'Q':
    		case 'q':
    			printf("Quit\n");
    			//QUIT();
    			break;
    
    		default:
    			printf("Invalid Option \n");
    			break;
    	}
    }
    Please help me see what is the problem, no matter that character or number I entered, the program also display Invalid Option.
    1. dont use void main,it returns int.
    2.just change scanf_s(i dont know what it is) to simply scanf.

  4. #4
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    Quote Originally Posted by BEN10 View Post
    1. dont use void main,it returns int.
    2.just change scanf_s(i dont know what it is) to simply scanf.
    scanf_s is the "safe" version of scanf() promoted by MS - I'm not entirely sure how or why it's safer tho'.

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  5. #5
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    s_scanf reads from an array right not normal int ?

  6. #6
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    i hope this helps
    i used getchar in it for scanning the char
    Code:
    #include <stdio.h>
    #include <ctype.h>
    int main(void){
        char c;
        for(;;){
            puts("AIRLINE RESERVATION SYSTEM \n"
    	          "P - to Purchase Ticket \n"
                  "V - to View Arrangement \n"
    	          "Q - to Quit the system \n"
    	          "Enter the option : ");
            c=getchar();
            c=toupper(c);
            switch(c){
                case 'P':
                     puts("Purchase\n");
                     break;
                case 'V':
                     puts("View\n");
                     getchar();
                     break;
                case 'Q':
                     printf("Quit\n");
                     getchar();
                     break;
    	    default:
    			puts("Invalid Option \n"
    			         "Menu again\n");
    			continue;}
    			break;}
        return 0;
    }

  7. #7
    C++まいる!Cをこわせ! Elysia's Avatar
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    Quote Originally Posted by lolguy View Post
    s_scanf reads from an array right not normal int ?
    It reads from a string, yes.
    scanf_s reads from the input (similar to scanf).
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.
    For information on how to enable C++11 on your compiler, look here.
    よく聞くがいい!私は天才だからね! ^_^

  8. #8
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    Quote Originally Posted by Elysia View Post
    It reads from a string, yes.
    scanf_s reads from the input (similar to scanf).
    why is it safer than scanf ?

  9. #9
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    I believe it checks the syntax of the format string. Read more about it here.

  10. #10
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    Thx for help, now I learn more about C Programming, thx for giving solution and suggestion ^^

  11. #11
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    Hello

    Just replace scanf_s ---> scanf.
    it will work fine.

    Regards,
    Swetha

  12. #12
    C++まいる!Cをこわせ! Elysia's Avatar
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    Yes, but is there a need for it? The program will work the same regardless, so there's no point.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.
    For information on how to enable C++11 on your compiler, look here.
    よく聞くがいい!私は天才だからね! ^_^

  13. #13
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    From what I heard, scanf_s (for example) takes an additional buffer size parameter after every "%s". Microsoft claims that it is safer because the compiler will complain if you don't specify the buffer size.

    I don't see why couldn't they just warn whenever a "%s" is used without a field width ("%10s")...

    I'm gonna say it's just another Microsoft attempt at vendor lock-in.

    So I suggest changing it back to scanf for standard compliance (unless there is something I missed).
    Last edited by cyberfish; 04-23-2009 at 12:50 AM.

  14. #14
    C++まいる!Cをこわせ! Elysia's Avatar
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    Quote Originally Posted by cyberfish View Post
    I'm gonna say it's just another Microsoft attempt at vendor lock-in.
    But it isn't. It performs additional security checks that scanf doesn't.

    So I suggest changing it back to scanf for standard compliance (unless there is something I missed).
    I suggest not changing it. For standards compliance, all they have to do is add #define scanf_s scanf.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.
    For information on how to enable C++11 on your compiler, look here.
    よく聞くがいい!私は天才だからね! ^_^

  15. #15
    CSharpener vart's Avatar
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    Quote Originally Posted by Elysia View Post
    But it isn't. It performs additional security checks that scanf doesn't.



    I suggest not changing it. For standards compliance, all they have to do is add #define scanf_s scanf.
    And why standards cometee should follow Microsoft and not the opposite?
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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