问题
For example I want to do some thing when some combination of Ctrl key with any other key is pressed (or it may be Alt key).Then from the standard input how to read that key combination in C program as an input.
I tried with simple getchar() to know the ASCII values of these combinations. But it was some 1 to 25 and some other values for some key combinations. Is there any standard library function to read them. Dont ask me why do you want to do that.
Edit: My platform is Turbo C on Windows.
回答1:
The short answer: In a platform specific way.
The long answer: C's Input/Output concept is that of the streams standard output and standard input. The getchar() function that you mentioned above simply reads from the standard input stream. C doesn't have any notion of keyboards, despite keyboards being a common input method. There are normally several layers of abstraction between your keyboard and what gets passed through to standard input in your C program. The mechanism to do this is implementation defined, and not part of C at all. You mentioned ASCII, but C doesn't require ASCII despite it being extremely common.
Some libraries attempt to provide portable keyboard input facilities, such as SDL and curses.
See also the comp.lang.c FAQ on system dependencies, particularly 19.5.
回答2:
Here are the Windows Virtual-Key Codes -- your program gets them with GetMessage.
回答3:
//Here is a program to save a graphical o/p to bmp
#include<graphics.h>
#include<conio.h>
#include<stdio.h>
#include<stdlib.h>
int SaveBMP16(char []);
typedef unsigned char byte;
typedef unsigned int word;
typedef unsigned long dword;
void main()
{
/* request auto detection */
int gdriver;
int gmode, errorcode;
detectgraph(&gdriver,&gmode);
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "c:\\tc\\bgi");
errorcode = graphresult();
if (errorcode != grOk) /* an error occurred */
exit(1);
int midx, midy,radius = 100;
midx = getmaxx() / 2;
midy = getmaxy() / 2;
setcolor(getmaxcolor());
/* draw the circle */
circle(midx, midy, radius);
/* clean up */
SaveBMP16("Circle.Bmp");
}
struct BMP
{
// BitMap File Header
byte bfType[2]; /* 1 2 must always be set to 'BM' to declare that this is a .bmp file.*/
dword bfSize; /* 3 4 specifies the size of the file in bytes.*/
word bfReserved1;// 7 2 must always set to zero. */
word bfReserved2;// 9 2 must always be set to zero.
dword bfOffset; // 11 4 specifies the offset from the beginning of the file to bitmap data.
// BitMap Image Header
dword biSize; // 15 4 specifies the size of the BitMap Header structure, in bytes.
dword biWidth; // 19 4 specifies the width of image, in pixels.
dword biHeight; // 23 4 specifies the height of image, in pixels.
word biPlanes; // 27 2 specifies the number of planes of the target device,must be set to 0
word biBitCount; // 29 2 specifies the number of bits per pixel.
dword biCompression; //31 4 Specifies the type of compression, usually set to 0 - No Compres
dword biSizeImage; // 35 4 specifies the size of the image data, in bytes. If there is no compression, it is valid to set this member to zero.
dword biXPelsPerMeter; //39 4 specifies the the horizontal pixels per meter on the designated targer device, usually set to zero.
dword biYPelsPerMeter; // 43 4 specifies the the vertical pixels per meter on the designated targer device, usually set to zero
dword biClrUsed; // 47 4 specifies the number of colors used in bitmap, if set to 0 number of colors is calculated using the biBitCount member.
dword biClrImportant; // 51 4 specifies the number of color that are 'important' for the bitmap, if set to zero, all colors are important.
};
int SaveBMP16(char file[])
{
int i=0, j=0, r, g, b;
FILE *fp;
BMP *bmp;
bmp=(BMP *)malloc(54);
bmp->bfType[0]='B';
bmp->bfType[1]='M';
bmp->bfSize=153718;
bmp->bfReserved1=0;
bmp->bfReserved2=0;
bmp->bfOffset=118;
bmp->biSize=40;
bmp->biWidth=640;
bmp->biHeight=480;
bmp->biPlanes=1;
bmp->biBitCount=4;
bmp->biCompression=0;
bmp->biSizeImage=153600; //Fixed Size ?
bmp->biXPelsPerMeter=0;
bmp->biYPelsPerMeter=0;
bmp->biClrUsed=0;
bmp->biClrImportant=0;
fp=fopen(file, "wb");
if(fp == NULL)
{
printf("File can't be open");
getch();
return 1;
}
fwrite(bmp, 54, 1, fp);
fseek(fp, 54L, SEEK_SET);
// Upto Here its OK.
// Question 1. What do next 16x4 Lines do ?
fputc(0x0, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(127, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(127, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(127, fp);
fputc(127, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(127, fp);
fputc(0x0, fp);
fputc(127, fp);
fputc(0x0, fp);
fputc(127, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(192, fp);
fputc(192, fp);
fputc(0x0, fp);
fputc(192, fp);
fputc(192, fp);
fputc(192, fp);
fputc(0x0, fp);
fputc(128, fp);
fputc(128, fp);
fputc(128, fp);
fputc(0x0, fp);
fputc(255, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(255, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(255, fp);
fputc(255, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(255, fp);
fputc(0x0, fp);
fputc(255, fp);
fputc(0x0, fp);
fputc(255, fp);
fputc(0x0, fp);
fputc(0x0, fp);
fputc(255, fp);
fputc(255, fp);
fputc(0x0, fp);
fputc(255, fp);
fputc(255, fp);
fputc(255, fp);
fputc(0x0, fp);
i=0;
j=479;
fseek(fp, 118, SEEK_SET);
while(j>=0)
{
i=0;
while(i<640)
{
fputc((getpixel(i, j)<<4) | getpixel(i+1, j), fp); //Que 2. What does this do ? Why Left Shift 4 times and why Bit wise ORing of two pixles.
i+=2;
}
j--;
}
free(bmp);
fclose(fp);
return 0;
}
来源：https://stackoverflow.com/questions/471980/how-to-read-or-capture-ctrlsome-key-or-altsome-key-in-c