Introduction

Hello. It's guu.

This time, I've compiled an episode about ASCII code, one of the things you need to know when learning the C language.

One day during my training, I came across something called ASCII code.

Description: "Integer representation of numbers, letters, symbols, etc."

Guu "Hmm..."

When I learned about ASCII code for the first time, I had only this kind of impression.

However, I later found out that the ASCII code is actually very important.

Consider the following problem.

[Problem] Assign an integer to the variable num defined as a char type and output it with printf ( “ %d ” );

However, make sure that the output value is the same as the input value.

*Hint: Subtract ' 0 ' from num.

I don't really understand, so I made the following program for the time being.

#include <stdio.h> int main(void) { char num; // char型の変数 num を定義 printf (“ 整数を入力してください ”); //コマンドラインから整数を入力 num = getchar ( ); //入力した整数を num に代入 printf ( “ num : %d ” , num ); // 10進数で num を表示 return 0; }

Now that you have a program, compile and run it!

I tried typing 1 from the keyboard.

What value will be output? ?

-------------------------------------------------- --- output result

-----------------------------------------------------

guu "????????????"

Why is the number 49 printed instead of 1...?

I panicked at once.

Commentary

The point this time is that "1" was input with getchar() and output with printf ("%d");.

Printf ( “ %c ” ); is commonly used to print what is input with getchar( ).

%c outputs the input value (character) as a character.

But in this case we have to use printf ( “ %d ” ); as the output.

%d は入力された値を 10 進数表示（数字）で出力します。

 

in short…

If you enter "1" in the program below, "1" will be output as a character.

#include <stdio.h> int main(void) { char num; // char型の変数 num を定義 printf (“ 整数を入力してください ”); 　 //コマンドラインから整数を入力 num = getchar(); //入力した整数を num に代入 printf ( “ num : %c ” , num ); // 文字として num を表示 return 0; }

In this problem, I input "1" with getchar() and output it in decimal using printf ("%d");.

The input and output values did not match because the input and output formats were different.

 

Guu "But why did 49 come out when I input 1?"

 

This is where ASCII code comes into play.

But! !

Up to here for this time.

 

In the next blog of Guu, I will clarify the reason "Why 49 was output"!

Look forward to it (^^)

Summary

When assigning a number to a variable of type char via getchar( ), it is treated as a "character".

When I output what I input as a character with printf ( “ %d ” );

bridge to next time

Let's take a look at the ASCII code table! ASCII code table is here (^o^)