Your computer consists of several devices. These include a key-board, a display screen, one or more disc drives, possibly a printer, and the computer itself with its internal memory.
The keyboard: Basic runs on many different computers. Some have built-in keyboards, whereas others require that a separate terminal be added. What is more, the keyboards themselves vary from one computer to another. The letters and numbers are standard, but from that point on, there are many possible variations.
Return: when you have finished typing a line and wish to transfer it to the computer’s memory, you press the return key on many terminals the name of this key is Enter or Rent. Throughout this book we will always use the term to return when referring to this key. Pressing the return key also moves to you to the next line.
Shift and caps lock: the shift key has the same function on computer that it has on a typewriter. It causes either an uppercase letter to be printed or the upper symbol to be printed if there are two symbols on the key (as with the numbers and punctuation marks). The caps lock key affects only the letters, causing uppercase letters to be printed. Once pressed the caps lock key stays in effect until it is released by a second pressing.
Control: The Control or CTRL key is similar to the shift key. When press together with another character, it causes a special message to be sent to the computer instead of the character printed on the key. But in general, these control characters are not transmitted to the screen and their messages are not apparent to the operator. We will elaborate on control characters in later articles. In this, control characters are written as CTRL-X or X to indicate holding down the CTRL key and any other letter. (In this case X).
If your terminal does not have the CTRL key, there will be combination of keys to press to perform this function. You will have to consult the manual that comes with your terminal to determine what they are.
Backspace and delete: Again, your terminal may or may not have these keys. The backspace and delete keys will both delete the character immediately to the left of the cursor. These keys are most commonly used for correcting typing errors before the return key is pressed. If your keyboard does not have these keys, your manual will tell you the combinations of keys to press to perform these functions. Older versions of CP/M do not recognize the backspace key. If you have CP/M version 2.0 or later, you will find the backspace key much easier to use than the delete key.
Repeat: Many terminals have a repeat key. When a particular key is pressed at the same time as the repeat key, the character represented by the first key repeats rapidly until the repeat key is released. On other terminals, simply holding down any key will cause the character it represents to repeat after a short period of time. The repetitions stop when the key is released.
Escape: The Escape key is used in editing Mbasic programs while in the edit mode. When you are interesting characters, the escape key tells Mbasic that you are through inserting characters and that any text you enter is to be considered as edit commands. This key may be labeled ESC or ALT on your key board.
Tab: The tab key works like its counterpart on a typewriter. TAB stops are usually set at every eight columns. Pressing the TAB key will move the cursor to the right, bringing it to the next tab stop. The Tab key is used mainly for aligning program statements or output for better readability. The Tab key otherwise acts much like the spacebar.
Line Feed: Pressing Line Feed causes the cursor to move down one line on the screen. But in contrast to the Return key, Line Feed does not cause the material you are entering to be transferred to the computer’s memory. Line feed is used when you are entering a line in an Mbasic program that is greater in length than the number of columns that your terminal supports. When you have finished entering the material, which may be on two or more lines, the return key must be pressed.