Thread: simple calculator problem...

below is my calculator programming.I want to make it show "maths error" when any number divided by 0, but i get any number +,-,*,/ by 0 also get maths error.I need u guys to correct my program,please.

Code:

#include <stdio.h>


int main()
{
    float num1, num2;
    char operation;
    while (1) {
        scanf("%f%c%f", &num1, &operation, &num2);
        if (operation == '+')
            printf("%f\n", num1+num2);
        if (operation == '-')
            printf("%f\n", num1-num2);
        if(operation == '*')
            printf("%f\n", num1*num2);
        if (num2 == 0)
        {
            printf ("maths error\n");
        }
        else if (operation == '/')
            printf("%f\n", num1/num2);
    }
    return 0;
}

You need to look at how the if statements are evaluated. The way your code looks now, it will always check if num2 is equal to zero, even if you are using the +, - or * operator.

What you want to do is probably something like:

Code:

if (operation == '+') {
    /* do + stuff */
} else if (...) {
    /* .... */
} else if (operation == '/') {
    /* check for division by zero */
}

If you don't want all those if-statements lining up, you could look into using a switch-statement instead for checking the operator.

iceaway, thanks so much!i got it!

Code:

#include <stdio.h>


int main()
{
    float num1, num2;
    char operation;
    while (1) {
        scanf("%f%c%f", &num1, &operation, &num2);
        if (operation == '+')
            printf("%f\n", num1+num2);
        else if (operation == '-')
            printf("%f\n", num1-num2);
        else if(operation == '*')
            printf("%f\n", num1*num2);
        else if (num2 == 0)
        {
            printf ("maths error\n");
        }
        else if (operation == '/')
            printf("%f\n", num1/num2);
    }
    return 0;
}

now i want my calculator to show in 2 decimal place, what command should i put?

Why is Google so underused again?
float - Rounding Number to 2 Decimal Places in C - Stack Overflow

Can't, it's too small to read.

i have no idea how to make it bigger, because i just print screen from the microsoft word. please download below attachment and help me check.

Attachment 10913

Your attachment attempt #2 doesn't work "Invalid attachment".

Your pseudo code should have indentation (like your code should have), on all subordinate lines of code.

The amount that a line is indented from a previous line should never by more than 2 to 5 spaces. (and spaces work more reliably on the board, then tabs do).

code tags - use 'em always for code and pseudo code. highlight your code, and in the advanced editor, click on the # icon near the upper right hand corner of the editor.

[code ]

Code:

 
if(you don't have code tags and indentation)
   printf("Your code will be hard to read/study\n");

[/code ]

Code tags are just like the what you see above EXCEPT they don't have a space after the e.

Originally Posted by yeohwl91

Code:

scanf (mathematical expression)
if (calculation is not division)then (go to the calculating and round off value into 2 decimal places)
if (calculation is division)
then (check whether denominator is zero)
else if (denominator is zero)
then (show "maths error")
else if (denominator is not zero)
then (go to the calculating and round off value into 2 decimal places)
if end
printf (show answer)

The above isn't pseudo code for your program. Just paraphrase your actual program, line by line.

Don't rearrange the order of the logic.

Code:

print out Enter Calculation
scan the maths expression
if operation is addition
then print out number 1+number 2=answer
else if operation is substraction 
then print out number 1-number 2=answer
else if operation is multiplication
then print out number 1*number 2=answer
else if number 2 is zero
then print maths error
else if operation is division
then print out number 1/number 2=answer

How to write pseudo code for "#include <stdio.h>, int main (), float, char operation,while (1) and return 0?