IntermediatePractice in the editor

Turbo C: conio.h and graphics.h

Many schools still teach C with Turbo C, an old compiler for MS-DOS with two famous extra headers: conio.h for coloured text and key presses, and graphics.h for drawing. They are not part of standard C, but our editor supports them, so those programs run in your browser.

conio.h: colours and keys

ExampleTry it in the editor

#include <conio.h>
#include <stdio.h>

int main(void) {
    clrscr();                     // clear the screen
    textcolor(YELLOW);
    cprintf("Welcome to Turbo C style programs!");
    textcolor(WHITE);
    gotoxy(5, 3);                 // column 5, row 3
    cprintf("Press any key...");
    getch();                      // wait for one key, without Enter
    return 0;
}

You type

Function	Does
`clrscr()`	clears the screen
`gotoxy(x, y)`	moves the cursor (columns and rows from 1)
`textcolor(c)`, `textbackground(c)`	sets the colours for `cprintf`
`getch()`	reads one key without showing it or waiting for Enter
`kbhit()`	tells whether a key is waiting, without stopping

graphics.h: drawing

initgraph opens a graphics window of 640 by 480 pixels with 16 colours; (0, 0) is the top-left corner and y grows downwards. closegraph closes it.

ExampleTry it in the editor

#include <conio.h>
#include <graphics.h>

int main(void) {
    int gd = DETECT, gm;
    initgraph(&gd, &gm, "");

    setfillstyle(SOLID_FILL, LIGHTBLUE);
    bar(0, 0, 639, 330);                  // sky
    setfillstyle(SOLID_FILL, GREEN);
    bar(0, 331, 639, 479);                // grass
    setcolor(YELLOW);
    circle(540, 80, 40);                  // sun
    setfillstyle(SOLID_FILL, YELLOW);
    floodfill(540, 80, YELLOW);
    setcolor(WHITE);
    rectangle(200, 220, 360, 360);        // house
    line(200, 220, 280, 150);             // roof
    line(280, 150, 360, 220);
    outtextxy(20, 20, "My first drawing in C");

    getch();
    closegraph();
    return 0;
}

You type

Common functions: line, circle, rectangle, bar, ellipse, arc, putpixel, floodfill, outtextxy, setcolor and setfillstyle. getmaxx() and getmaxy() return 639 and 479, the last pixel in each direction.

Animation

Clear the screen, draw the next frame, wait a little with delay from dos.h, and repeat. kbhit lets the user stop it:

ExampleTry it in the editor

#include <conio.h>
#include <dos.h>
#include <graphics.h>

int main(void) {
    int gd = DETECT, gm;
    initgraph(&gd, &gm, "");
    for (int x = 40; x < 600 && !kbhit(); x += 8) {
        cleardevice();
        setfillstyle(SOLID_FILL, LIGHTRED);
        fillellipse(x, 240, 25, 25);
        delay(30);
    }
    closegraph();
    return 0;
}

Old style and modern style

Turbo C programs often write void main(). Our editor runs it but warns: standard C requires int main(void) and return 0. Use the modern form in new programs, and remember that conio.h and graphics.h exist only in some compilers; standard C programs use printf and scanf.

Practice exercises

Draw a traffic light: a dark rectangle with red, yellow and green circles.
Draw a bar chart of five values with bar and label each bar with outtextxy.
Move a ball from left to right and back again until a key is pressed.