[C language] getchar() and scanf(), EOF, realize the uppercase and lowercase conversion of letters. Multiple sets of input and output

Implements case conversion of letters. Multiple sets of input and output

example

A
B
a
b

Table of contents

getchar() 

scanf()

EOF 

getchar() 

#include<stdio.h>
int main() 
{

    int ch = 0;
    while (ch = getchar()) 
    {
        putchar(ch+32);
    }
    return 0;
}

Because 

From the keyboard, type A and enter (\n) to the buffer, getchar first takes A from the buffer (A+32 corresponds to a in the ASCII table), and takes \n from the buffer (\n+ 32 corresponds to *) in the ASCII table

So the output is: a*

Solution:

Use another getchar() to read the carriage return

int main() 
{
    int ch = 0;
    // EOF: end of file 
    //想让循环停止:Ctrl+Z
    while ((ch = getchar()) != EOF)
    {
        putchar(ch+32);
        getchar();//用来读取\n
        printf("\n"); //换行
    }
    return 0;
}

 Improve

#include<stdio.h>
int main()
{
    int ch = 0;
    while ((ch = getchar()) != EOF)
    {
        printf("%c\n",ch+32);
        getchar();//用来读取\n   
    }
    return 0;
}

scanf()

#include <stdio.h>

int main() {
    char ch = 0;
    while(scanf("%c ",&ch) != EOF)
    {
        printf("%c\n",ch+32);
    }
    return 0;
}

Regarding ~scanf() for multiple sets of input in a while loop

 

#include <stdio.h>

int main() {
    char ch = 0;
    while(~scanf("%c ",&ch))
    {
        printf("%c\n",ch+32);
    }
    return 0;
}

EOF 

EOF goes to the definition in C language and its value is (-1), end of file, the end of the file.

EOF is returned by an I/O routine when the end-of-file (or in some cases, an error) is encountered.

Meaning: when end-of-file (or in some cases, error) is encountered, the I/O process returns EOF.

When performing multiple sets of input in the terminal, press Ctrl+Z to stop the input.

• ~ This is a c language operator, bitwise negation.

 

Both while(scanf("%c",&ch) != EOF) and while(~scanf("%c",&ch)) can perform multiple sets of input and output.