scanf 可以使用“%c”而不是“%s”扫描多个字符，为什么？

Question

此代码会从用户接收未知数量的字符，直到他输入“;”然后打印一堆有关字符的信息。 我的问题是为什么扫描一个字符能够接收多个字符的输入，我认为一个字符的 scanf 仅适用于一个字符并且能够扫描多个字符我需要使用“%”扫描字符串或数组s”。

  Include files:
--------------------------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>


/*=========================================================================
  Constants and definitions:
==========================================================================*/

/* put your #defines and typedefs here*/

void printGivenParamsToTheOutput( char ch, int asciiCode, int asciiCodePowTwo,
                                  int difference, int unitDigitOfDiff );

void printResults(int digitsCounter, int lettersCounter, int spacesCounter);


/*-------------------------------------------------------------------------
  The main program. (describe what your program does here)
 -------------------------------------------------------------------------*/
int main() {
    char ch = 0;
    int privNumChar=0, dif=0, lastDigDif=0, numDig=0, numLett=0, numSpac=0;
    do {
        scanf("%c", &ch); //asking for characters to analysis
        if (ch == ';') { //';' ending the program running
            break;
        }
        else {
            // difference between current number to the previous one
            dif = ch - privNumChar;
            privNumChar = ch;
            //calculating the difference last digit
            lastDigDif = dif%10;
            printGivenParamsToTheOutput(ch, ch, ch, dif, lastDigDif);
            //calculating how many times each type appeared in the message
            if (('a'<=ch && ch<='z') || ('A'<=ch && ch<='Z')) { ++numLett; }
            else if ('0'<=ch && ch<='9') { ++numDig; }
            else if (ch == ' ') { ++numSpac; }
        }
    }
    while (ch != ';');

    printResults(numDig, numLett, numSpac);
    return 0;
}

 void printGivenParamsToTheOutput (char ch, int asciiCode, int asciiCodePowTwo,
                                    int difference, int unitDigitOfDiff){
    asciiCodePowTwo = ch*ch; //calculating ascii value raising to a power
    printf( "%c%10d%10d%10d%10d\n", ch, asciiCode, asciiCodePowTwo,
            difference, unitDigitOfDiff );
}


void printResults(int digitsCounter, int lettersCounter, int spacesCounter){
    printf("Number of digits received: %d\n", digitsCounter);
    printf("Number of letters received: %d\n", lettersCounter);
    printf("Number of spaces received: %d\n", spacesCounter);
}

Answer 1

你有

do {
    scanf("%c", &ch); //asking for characters to analysis
    //some further code
while (ch != ';');

现在，您正在重复将字符读入

ch

，直到

;

的结束符号。您不是通过一次

scanf

调用来完成此操作，而是重复调用它，直到收到

;

的结束信号。

尝试调试代码并查看每次

ch

会遇到什么情况，然后您会发现您关于

scanf

每次调用

char

接收单个

%c

的假设得到遵守。