getchar

while (getchar () != '\n' );

由 喜你入骨 提交于 2019-12-19 05:11:10
问题 I have the following for loop, I am prompting the user to enter a 4 digit pin and hit enter. Can someone explain to me what the while loop is really doing because I don't fully understand it. //user input for pin for(i = 0; i < PIN_LENGTH; i++) { printf("Enter digit %d of your PIN: ", i); user_pin[i] = getchar(); while (getchar() != '\n'); //what is this line doing?? } 回答1: When you give input to the program, then you end it with the Enter key. This key is sent to your program as a newline.

EOF exercise 1-6 K&R The C programming language

由 假装没事ソ 提交于 2019-12-19 04:06:02
问题 This is taken directly from the K&R book: The precedence of != is higher than that of = , which means that in the absence of parentheses the relational test != would be done before the assignment = . So the statement c = getchar() != EOF is equivalent to c = (getchar() != EOF) This has the undesired effect of setting c to 0 or 1, depending on whether or not the call of getchar returned end of file. (More on this in Chapter 2.) Exercise 1-6. Verify that the expression getchar() != EOF is 0 or

Is getchar() equivalent to scanf(“%c”) and putchar() equivalent to printf(“%c”)?

由 梦想的初衷 提交于 2019-12-18 11:58:21
问题 Is a = getchar() equivalent to scanf("%c",&a); ? Is putchar(a) equivalent to printf("%c",a); where a is a char variable? 回答1: Generally speaking yes they are the same. But they are not in a few nitpicky ways. The function getchar is typed to return int and not char . This is done so that getchar can both all possible char values and additionally error codes. So while the following happily compiles in most compilers you are essentially truncating away an error message char c = getchar(); The

Why is getchar() reading '\n' after a printf statement?

由 走远了吗. 提交于 2019-12-18 04:26:13
问题 I'm prompting the user to enter the length of an array, initializing a char[] array with this input, and then prompting the user to type a message to enter into the char[] array. I'm reading the first character of the user's message with getchar() . However, getchar() is reading the new-line escape '\n' before it is reading any user input. It seems to be getting '\n' from the previous printf statement that prompts the user... Here is the relevant code: #include <stdio.h> int main(void) { int

getchar() returns the same value (27) for up and down arrow keys

由 眉间皱痕 提交于 2019-12-17 20:26:17
问题 So for the up key on the keyboard, I get 27, surprisingly for the down key I also get 27. I need my program to behave differently on the up and down key, and I can't seem to figure it out. I am using Linux, and need it to work for Linux. #include <stdio.h> #include <stdlib.h> #include <string.h> #include <ctype.h> int main() { int c = getchar(); if(c==27) { printf("UP"); } if(c==28) { printf("DOWN"); } } 回答1: The 27 implies that you're getting ANSI escape sequences for the arrows. They're

Cannot figure out how to use getchar(); in C

由 ℡╲_俬逩灬. 提交于 2019-12-17 18:59:36
问题 #include <stdio.h> int main(void) { char F,C; printf("Do you have a Fever? y/n\n"); F = getchar(); printf("Do you have a runny nose or cough? y/n\n"); C = getchar(); printf("Here are the results you input:\n"); printf("Do you have a fever?"); putchar(F); printf("\nDo you have a runny nose or cough?"); putchar(C); return 0; } The code inputs results from first getchar(); and then exits without waiting for more input. Why is that? 回答1: Use a while loop after each getchar() if you want to

Theory Behind getchar() and putchar() Functions

由 徘徊边缘 提交于 2019-12-17 16:31:29
问题 I'm working through "The C Programming Language" by K&R and example 1.5 has stumped me: #include <stdio.h> /* copy input to output; 1st version */ int main(int argc, char *argv[]) { int c; while ((c = getchar()) != EOF) putchar(c); return 0; } I understand that 'getchar()' takes a character for 'putchar()' to display. However, when I run the program in terminal, why is it that I can pass an entire line of characters for 'putchar()' to display? 回答1: Because your terminal is line-buffered.

Why Ctrl-Z does not trigger EOF?

由 喜你入骨 提交于 2019-12-17 09:57:52
问题 Why Ctrl + Z does not trigger the loop to finish on the following small program? #include <stdio.h> main() { int c; while ((c = getchar()) != EOF) { //nothing } return 0; } If I enter: test^ZEnter , it does not get out of the loop. I found related questions around (here and here) but none to explain it for C (not C++) under Windows. Note : I use Visual Studio 2015 PRE on a windows 8.1 回答1: You need to hit Enter and then use ctrl + Z and then Enter again. or, you may also use F6 回答2: EOF like

Clarification needed regarding getchar() and newline

由 醉酒当歌 提交于 2019-12-17 04:35:21
问题 I have a doubt regarding using getchar() to read a character input from the user. char char1, char2; char1 = getchar(); char2 = getchar(); I need to get 2 chars as inputs from the user. In this case, if the user enters the character 'A' followed by a newline , and then the character 'B' , what will be stored in char2 - will it be the newline character or the character 'B' ? I tried it on CodeBlocks on Windows, and char2 actually stores the newline character, but I intended it to store the

字符数据的非格式化输入输出

由 主宰稳场 提交于 2019-12-17 03:33:11
1. 字符数据的非格式化输入 (1) getchar函数 int getchar() // stdio.h 功能：读取用户的按键信息，返回值是用户所键入的ASCII码。 该函数没有参数，有一个int型返回值。当调用getchar时，程序就等待用户按键。用户输入的字符将被存放到键盘缓冲区中，知道用户按回车键为止（回车字符也将存放到缓冲区中）。getchar函数的返回值是用户输入的第一个字符。如果用户在按回车键前，输入了不止一个字符，则其他字符将保留在键盘缓冲区中，等待后续getchar调用来读取。也就是说，后续的getchar调用不会再等待用户按键，而直接读取缓冲区中的字符，直到缓冲区中的字符读取完后，才等待用户按键。用getchar函数接受字符输入时，字符会显示在屏幕上。 (2) getc函数 int getc(FILE *stream) // stdio.h 功能：从流文件stream中读取一个字符信息，它的返回值是所读取字符的ASCII码。 该函数带有一个参数stream，它是一个文件指针，表示流文件。当流文件是stdin时，getc函数的功能与getchar函数的功能完全相同。也就是说，getc(stdin)与getchar()等价。 (3) getche函数 int getche() // conio.h 功能：与getchar的功能基本相同。唯一的差别是
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