Computer terminal: Difference between revisions

Revision as of 16:25, 11 April 2019

Revision as of 16:27, 11 April 2019

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Programmers of block-oriented terminals often used the technique of storing ''context'' information for the transaction in progress on the screen, possibly in a hidden field, rather than depending on a running program to keep track of status. This was the precursor of the [[HTML]] technique of storing context in the [[URL]] as data to be passed as arguments to a [[Common Gateway Interface|CGI]] program.

Some keys on a block-oriented terminal function differently from the corresponding kes on a character-oriented terminal. For example, <code>TAB</code>, <code>BACKTAB</code>, <code>BACKSPACE</code>, and the cursor movement and editing keys such as <code>DELETE</code> typically perform a local function and are not transmitted to the host. The <code>TAB</code> key usually moves the cursor to the next enterable field.

Unlike a character-oriented terminal, where typing a character into the last position of the screen usually causes the terminal to scroll down one line, entering data into the last screen position on a block-oriented terminal usually causes the cursor to ''wrap''— move to the start of the first enterable field. Programmers might "protect" the last screen position to prevent inadvertent wrap. Likewise a protected field following an enterable field might lock the keyboard and sound an audible alarm if the operator attempted to enter more data into the field than allowed.