C programming

The BD Software C compiler is included on drive A: or drive B: if you have the CP/M filesystem loaded on the Micro SD card. The following text is an exert from the BDS C Wikipedia article.

BDS C (or the BD Software C Compiler) is a compiler for a sizeable subset of the C programming language, that ran on and generated code for the Intel 8080 and Zilog Z80 processors. It was the first C compiler for CP/M. It was written by Leor Zolman and first released in 1979 when he was 20 years old. "BDS" stands for "Brain Damage Software."

BDS C User's Guide

Refer to the BDS C User's Guide for more about the language and its implementation.

Compile C applications

The CP/M disk image includes a simple HW.C (Hello, world) application. BDS C language has support for Intel 8080 CPU input and output port instructions. The HW.C application displays the system tick count, UTC, and local date and time, and then sleeps for 1 second. For more information about Intel 8080 IO port mappings, refer to Intel 8080 input and output ports.

Follow these steps to list, compile, link, and run the HW.C file:

List the hw.c file

type hw.c

/* Copyright (c) Microsoft Corporation. All rights reserved.
   Licensed under the MIT License. */

/* C application to demonstrate use of Intel 8080 IO Ports */

main()
{
    unsigned c, l;
    char buffer[50];

    printf("\nHello from the Altair 8800 emulator\n\n");

    for (c = 0; c < 65535; c++)
    {
        printf("Count:%u\n", c);
        printf("System tick count: %s\n", get_port_data(41, buffer, 50));
        printf("UTC date and time: %s\n", get_port_data(42, buffer, 50));
        printf("Local date and time: %s\n\n", get_port_data(43, buffer, 50));

        sleep(1); /* Sleep for 1 second */
    }
}

/* Sleep for n seconds */
sleep(seconds)
char seconds;
{
    outp(30, seconds); /* Enable sleep for N seconds */
    while (inp(30)); /* Wait for sleep to expire */
}

/* Get data from Intel 8080 IO port */
char *get_port_data(port_num, buffer, buffer_len)
int port_num;
char *buffer;
int buffer_len;
{
    char ch;
    int index;

    index = 0;

    while ((ch = inp(port_num)) && index < buffer_len) {
        buffer[index++] = ch;
    }
    buffer[index] = 0x00;

    return buffer;
}

Compile the hw.c file:
```
cc hw
```
Link the hw application:
```
clink hw
```
Run the hw application:
```
hw
```
Stop the hw application by selecting Ctrl+C.

Editing hw.c with Word-Master

In the following steps use the Word-Master text editor to edit a file. It's highly recommended to edit files with Visual Studio Code and then copy the file to the Altair filesystem using the CP/M gf command.

Edit the hw.c file with Word-Master:
```
wm hw.c
```
Switch the web terminal to character input mode by selecting Ctrl+L.
Make your changes to the hw.c file.
Save your updates to the hw.c file:
1. Select the Esc key.
2. Select E to exit. Your file changes are saved to disk.
Switch the web terminal to line input mode by selecting Ctrl+L.
Then compile, link, and run the updated hw.c application.

C programming

BDS C User's Guide​

Compile C applications​

Editing hw.c with Word-Master​

BDS C User's Guide

Compile C applications

Editing hw.c with Word-Master