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Exploring ANSI Command Sequences for Terminal Emulation and Screen Management

This document delves into essential ANSI command sequences used in terminal emulation, particularly for console redirection. It covers commands for clearing the screen, repositioning the cursor, setting text attributes including colors, and controlling cursor visibility. Practical examples illustrate how these commands work, such as moving the cursor to specific screen coordinates and changing text colors. Additionally, it includes a demo program that showcases a protected-mode exception handler sending diagnostic information via a serial null-modem cable. Students are encouraged to modify existing C++ programs to enhance their functionality with ANSI commands.

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Exploring ANSI Command Sequences for Terminal Emulation and Screen Management

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  1. ANSI command-sequences A look at some terminal emulation features utilized in the “console-redirection” mechanism

  2. Clearing the screen • Here is an ANSI command-sequence that clears the terminal’s display-screen: char cmd[] = “\033[2J”; int len = strlen( cmd ); write( 1, cmd, len );

  3. Reposition the cursor • Here is an ANSI command-sequence that moves the cursor to row 12, column 40: char cmd[] = “\033[12;40H”; int len = strlen( cmd ); write( 1, cmd, len );

  4. ANSI color-codes 0 = black 1 = red 2 = green 3 = brown 4 = blue 5 = magenta 6 = cyan 7 = gray

  5. Setting text attributes • Here is an ANSI command-sequence that sets foreground and background colors: char cmd[] = “\033[32;44m”; int len = strlen( cmd ); write( 1, cmd, len );

  6. Cursor visibility commands • Here are ANSI command-sequences that will ‘hide’ or ‘show’ the terminal’s cursor: char hide[] = “\033[?25l”; // lowercase L char show[] = “\033[?25h”; // lowercase H

  7. Demo-program • We created a boot-time program (called ‘emitinfo.s’) that shows how a protected-mode exception-handler can send some diagnostic information via the serial null-modem cable to a remote machine that is running a ‘terminal emulator’ application

  8. In-class exercise • Modify this simple C++ program so that it will print its “Hello” message in colors and be located in the center of the screen: #include <stdio.h> int main( void ) { printf( “Hello, world! \n” ); }

  9. In-class exercise #2 and #3 • Modify the ‘emitinfo.s’ program so that it will also display the FS and GS registers • Modify the ‘emitinfo.s’ program so that its ‘isrGPF’ exception-handler will execute in 64-bit mode (on your ‘anchor’ machine)

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