Control characters:

While control characters have well defined meanings intended for terminals, BBS tradition has used these to display IBMs "low ascii" glyphs. Because of this historical usage, we must therefore support this if we intend to be compatible with a larger number of door games. In the standards, these are referred to as the C0 control function set.

List of all control characters by ASCII value

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NUL (0x00): (Subject to discussion)

No action. The NULL character is silently discarded. Traditionally, the NUL character has been used as a pad character by UNIX systems. Because of this historical usage, this must be retained.

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SOL (0x01):

This will display the "while smiling face" (☺) character which is unicode 9786 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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STX (0x02):

This will display the "black smiling face" (☻) character which is unicode 9787 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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ETX (0x03):

This will display the "black heart suit" (♥) character which is unicode 9829 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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EOT (0x04):

This will display the "black diamond suit" (♦) character which is unicode 9830 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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ENQ (0x05):

This will display the "black club suit" (♣) character which is unicode 9827 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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ACK (0x06):

This will display the "black spade suit" (♠) character which is unicode 9824 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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BEL (0x07):

Beep - Causes the terminal to make a beep sound. The duration and frequency of the beep is up to the implementor and a system "beep" should be used when possible. However, as a rough guide, 440Hz, 100ms duration has been used by some terminals.

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BS (0x08): (Subject to discussion)

Non-destructive backspace. Moves cursor position to the previous column unless the current column is the first, in which case no operation is performed.

DISCUSSION:

Since the left movement code is functionally identical to this behaviour, some feel that backspace should be destructive. If it is destructive, we will need to define if the previous character cells attributes are left as-is or changed to the current attributes. Further, many standard *nix programs (tcsh for example) assume it is not destructive. Additionally, the specification clearly defines a non-destructive backspace.

Source: http://www.ecma-inte rnational.org/publications/files/ECMA-ST/Ecma-048.pdf

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TAB (0x09): (Subject to discussion)

Moves to the next tab stop. Does not overwrite any characters in between. A tab will not cause advancing to the next line. Tab stops exist at positions 1, 9, 17, and every eight characters thereafter as well as at the last position on the li ne (generally column 80)

DISCUSSION:

• Perhaps the tab should advance to the next line.

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LF (0x0a):

Move cursor position to same column of the next row. If current row is the last row, scrolls the screen up and fills the new row with the current attribute.

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VT (0x0b):

This will display the "male sign" (♂) character which is unicode 9794 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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FF (0x0c):

Clears screen and homes cursor. Same as CSI2J.

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CR (0x0d):

Move cursor position to column 1 of the current line

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SO (0x0e):

This will display the "beamed eighth notes" (♫) character which is unicode 9835 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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SI (0x0f):

This will display the "white sun with rays" (☼) character which is unicode 9788 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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DLE (0x10):

This will display the "black right-pointing pointer" (▶) character which is unicode 9654 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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DC1 (0x11):

This will display the "black left-pointing pointer" (◀) character which is unicode 9664 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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DC2 (0x12):

This will display the "up down arrow" (↕) character which is unicode 8597 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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DC3 (0x13):

This will display the "double exclamation mark" (‼) character which is unicode 8252 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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DC4 (0x14):

This will display the "pilcrow sign" (¶) character which is unicode 182 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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NAK (0x15):

This will display the "section sign" (§) character which is unicode 167 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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SYN (0x16):

This will display the "black rectangle" (▬) character which is unicode 9644 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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ETB (0x17):

This will display the "up down arrow with base" (↨) character which is unicode 8616 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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CAN (0x18):

This will display the "upwards arrow" (↑) character which is unicode 8593 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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EM (0x19):

This will display the "downwards arrow" (↓) character which is unicode 8595 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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SUB (0x1a):

This will display the "rightwards arrow" (→) character which is unicode 8594 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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ESC (0x1b): (Subject to discussion)

This chacter is reserved for use to introduce control codes and control characters.

DISCUSSION:

It has been suggested that an ESC followed by a NUL should display the "leftwards arrow" (←) character which is unicode 8592 and occupies this slot on IBMs running codepage 437 and treated as a normal character.

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FS (0x1c): (Subject to discussion)

This will display the "turned not sign" (⌙) character which is unicode 8985 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

DISCUSSION:

It has been suggested that the far more common "right angle" (∟) which is unicode 8735 be used here. Apparently, IBM now uses this character in their maps.

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GS (0x1d):

This will display the "left right arrow" (↔) character which is unicode 8596 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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RS (0x1e):

This will display the "black up-pointing triangle" (▲) character which is unicode 9650 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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US (0x1f):

This will display the "black down-pointing triangle" (▼) character which is unicode 9660 and occupies this slot on IBMs running codepage 437. This will be treated as a normal character.

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DEL (0x7f):

Delete Character deletes the character at the current position by shifting all characters from the next column of the current line left to the current column. The opened blank at the end of the line is filled with the current attribute.

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