Using more than one if's sub routine in one program

**shan2014** · 03-20-2014

Can we use more than one 'if' subroutine in one program.
I am trying to implement this but if I run the two subroutines at the same time the lower subroutine directly shows "invalid grade". But if I run one at a time then they work perfectly fine.
Why is this happening? Does the compiler think that its the same "if" routine. If so how do I segregate it???

Code:

        printf("Enter a score:");
    scanf("%d",&gr);
    if(gr>=80 && gr<=100)
    printf("A Grade\n");
    if (gr>=60 && gr<80)
    printf("B Grade\n");
    if (gr>=40 && gr<60)
    printf("C Grade\n");
    if (gr>=20 && gr<40)
    printf("D Grade\n");
    if (gr<20)
    printf("E Grade\n");
    if(gr<0 && gr>100) 
    printf("invalid\n\n");
    


    printf("Enter a grade:\n");
    scanf("%c",&gre);
    if(gre=='A')
    printf("Range: 80 to 100 \n");
    if (gre=='B')
    printf("Range: 60 to 79 \n");
    if (gre=='C')
    printf("Range: 40 to 59\n");
    if (gre=='D')
    printf("Range: 20 to 39\n");
    if (gre=='E')
    printf("Range: 0 to 19\n");
    if (gre!='A'&& gre!='B'&& gre!='C'&& gre!='D'&& gre!='E') 
    printf("invalid grade\n\n");

**stahta01** · 03-20-2014

It is the "if" statement NOT "if" subroutine.

This is the line of code with the problem.

Code:

scanf("%c",&gre);

Change to

Code:

scanf(" %c",&gre);

The space before the "%" tells the scanf to skip over whitespace.
This includes the newline.

Tim S.

**africanwizz** · 03-20-2014

you need to clear the buffer after the first scanf(), the FAQ page has a nice page explaining this

**shan2014** · 03-20-2014

Originally Posted by stahta01

It is the "if" statement NOT "if" subroutine.

This is the line of code with the problem.

Code:

scanf("%c",&gre);

Change to

Code:

scanf(" %c",&gre);

The space before the "%" tells the scanf to skip over whitespace.
This includes the newline.

Tim S.

Huh! Can a space actually help the compiler to understand that it is a separate "if" statement

**shan2014** · 03-20-2014

Originally Posted by africanwizz

you need to clear the buffer after the first scanf(), the FAQ page has a nice page explaining this

Okay! I will check it out!

**stahta01** · 03-20-2014

Originally Posted by shan2014

Huh! Can a space actually help the compiler to understand that it is a separate "if" statement

No, but that is NOT the problem in your code.

Tim S.

**shan2014** · 03-20-2014

Originally Posted by stahta01

No, but that is NOT the problem in your code.

Tim S.

And it works like charm!
Thanks a lot !!!!

**anduril462** · 03-20-2014

Consider using else if to simplify this -- which you should try to do whenever you have mutually exclusive cases (i.e. a grade can't be both an A and a B at the same time). Start at the highest (invalid score, > 100) and work down:

Code:

#define MAX_SCORE 100
#define A_MIN_SCORE 80
#define B_MIN_SCORE 60
...
if (grade > MAX_SCORE)
    print "invalid"
else if (grade >= A_MIN_SCORE)
    print "A"
else if (grade >= B_MIN_SCORE)
...

Note a few things:

I used named constants to make your code easier to read, modify and maintain.
The else part of the else if ensures that all previous conditions checked are false. Thus if we work down (or up) in order, we only have to check the lower (or upper) limit of a range.
Technically this is a bit quicker too, as it will stop checking the if/else if conditions once it matches one. Your version checks every if, even

**shan2014** · 03-21-2014

Originally Posted by anduril462

Consider using else if to simplify this -- which you should try to do whenever you have mutually exclusive cases (i.e. a grade can't be both an A and a B at the same time). Start at the highest (invalid score, > 100) and work down:

Code:

#define MAX_SCORE 100
#define A_MIN_SCORE 80
#define B_MIN_SCORE 60
...
if (grade > MAX_SCORE)
    print "invalid"
else if (grade >= A_MIN_SCORE)
    print "A"
else if (grade >= B_MIN_SCORE)
...

Note a few things:

I used named constants to make your code easier to read, modify and maintain.
The else part of the else if ensures that all previous conditions checked are false. Thus if we work down (or up) in order, we only have to check the lower (or upper) limit of a range.
Technically this is a bit quicker too, as it will stop checking the if/else if conditions once it matches one. Your version checks every if, even

Wow. Thanks a lot! Really simplifies the code!

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