if-else statement

Question

My codes allows the user to enter in a score from 1 to 100, which will either tell them that the score is "Good", "OK", "Moron", or "Invalid".

But, when I compile these codes. The output has invalid in it too with the correct statement if it is more than 54.

For example :

if I enter in 55 it will say "OK" AND "Invalid".
if I enter in 54 it will just say "Moron".

Here are my codes:

#define _CRT_SECURE_NO_WARNINGS #include<stdio.h> #include<stdlib.h> void main() { int score; printf("Enter a Score"); scanf("%d", &score); if (score >=80 && score <= 100){ printf("Good\n",); } if (score >=55 && score <=79){ printf("OK\n",); } if (score >=1 && score <=54){ printf("Moron\n",); } else{ printf("Invalid\n"); } system("pause"); }

souslov · Accepted Answer · 2015-05-13 14:08:02Z

It is happening because instead of using one control flow you use multiple (thus if condition is met before the last if control flow (score >= 55 through score <= 100), else code from the last one is also executed). You can use else if branches:

if (score >= 80 && score <= 100){ printf("Good\n",); } else if (score >= 55 && score <= 79){ printf("OK\n",); } else if (score >= 1 && score <= 54){ printf("Moron\n",); } else { printf("Invalid\n"); }

You can also use nested if/else statements, but the solution above seems less cumbersome.

pmwood · Accepted Answer · 2015-04-28 00:44:18Z

Each if statement is a standalone conditional statement. Your example has three groups of conditional statements:

if (score >=80 && score <= 100)
if (score >=55 && score <=79)
if (score >=1 && score <=54) { ... } else { ... }

So if score has the value 55, it will match against #2 above and the else of #3.

One solution here would be to combine the above statements into one group. You can do this with else if.

e.g.

if (*expr*) { ... } else if (*expr*) { ... } else if (*expr*) { ... } else { ... }

John3136 · Accepted Answer · 2015-04-28 00:27:25Z

You have 2 if-else statements and both get executed. So you will do "something" for both of them. Walk through your code with score=55 and you'll find the problem.

2 solutions:

Make the ifs "standalone" (so only one will pass)
Add some elses to ensure only one of your branches executes.

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