Flags
ANSI
Program execution may be governed by certain indicators or Flags. These Flags may be set or not set (FALSE). There are three types of Flags: Condition, Pseudo Condition and Function.
Condition Flags
Four Condition Flags are available: EQUAL (or ZERO), LESS, OVER and EOS. The EQUAL (or ZERO) Flag indicates a test has matched or a mathematical instruction has generated a ZERO result. The LESS Flag may be used for testing relative sizes or values in a less than (<) fashion. However, the OVER Flag is not a greater than (>) evaluation. The EOS (End Of String) Flag determines when manipulation of a character string has reached certain limitations. These Flags are set to TRUE or FALSE as the result of certain instructions, described further in this chapter.
Pseudo Condition Flags
There is one Pseudo Condition Flag: the GREATER Flag. While not actually a Condition Flag, it has been included to ease programming. The TRUE condition of the GREATER Flag signifies that both the LESS and EQUAL (or ZERO) Flags are FALSE, while a FALSE GREATER Flag signifies that one or both of them are TRUE. Therefore, it may be used for greater than (>) testing.
Function Flags
There are also flags associated with forty Function Keys and eleven other Control Keys (Function Flags), and an all encompassing FKEY Flag. Though all of the following Function Flags are supported by the compiler, their support within a specific program or application may be limited by the terminal or system in use. All of the Function Flags, including the FKEY Flag, are cleared at the beginning of each KEYIN instruction. The appropriate Function Flag is set whenever a supported Function or Control Key is entered at the terminal. The FKEY Flag is also set when any of the Function Flags is set. Only one of the Function Flags may be set at a time since it is cleared once it has been tested and is TRUE or upon occurrence of another KEYIN. The FKEY Flag determines if any Function Flag has been set. Any test of the FKEY Flag clears all function key flags.
The Function Flags are as follows:
|
Flag |
Set when ... |
|
FKEY |
any of the following are depressed. |
|
Fnn |
`nn' corresponds to function keys 1 to 40. |
|
UP |
the UP arrow key was depressed. |
|
DOWN |
the DOWN arrow key was depressed. |
|
LEFT |
the LEFT arrow key was depressed. |
|
RIGHT |
the RIGHT arrow key was depressed |
|
INS |
the INSert key was depressed. |
|
DEL |
the DELete key was depressed. |
|
PGUP |
the PAGE UP key was depressed. |
|
PGDN |
the PAGE DOWN key was depressed. |
|
HOME |
the HOME key was depressed. |
|
END |
the END key was depressed. |
|
ESC |
the ESCAPE key was depressed. |
|
ESCAPE |
the ESCAPE key was depressed. |
|
TAB |
the TAB key was depressed. |
|
BACKTAB |
the Shifted TAB key was depressed. |
|
EVENT |
an object event has occurred (PLBCMP GUI environment only) |
See Also: Program Control Instructions
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