DESCRIPTION
ASCII is a standard binary code used to represent character
data on computers. Most existing computers, printers,
terminals, etc. use the ASCII code to communicate with each
other. Older IBM systems such as 360 family mainframes use
another code called
EBCDIC
(Extended Binary Coded Decimal Interchange Code).
The standard ASCII code uses 7 bits to represent each
character. This provides codes from 0000000 to 1111111 (0 to
127 decimal). Modern computers use an 8 bit ASCII
character, although the latter codes, 10000000 to 11111111
(128 to 255 decimal) are not standardized.
Codes 00000000 to 00011111 (0 to 31 decimal) are the
control characters.
These characters has various
effects on printers and terminals. For example,
sending a line-feed (LF) character to a printer causes the
paper to scroll. Sending the same character to an ASCII
terminal will cause the cursor to move down, the analog to a
paper scroll on a printer. If the cursor is already at the
bottom of the screen, then the screen will scroll up. The
following is a list of the control characters and their purpose:
Name Decimal code Function
NUL 0 No effect - marker or delay
SOH 1 Start of header
STX 2 Start of text
ETX 3 End of text flag
EOT 4 End of transmission flag
ENQ 5 Enquiry
ACK 6 Positive acknowledgement
BEL 7 Ring printer or terminal bell
BS 8 Backspace - move left
HT 9 Horizontal TAB - Move right to next tab stop
LF 10 Line feed
VT 11 Vertical TAB
FF 12 Form feed (new page)
CR 13 Carriage return - go to left margin
SO 14 Shift out
SI 15 Shift in
DLE 16 Data link escape
DC1 17 Device control 1
DC2 18 Device control 2
DC3 19 Device control 3
DC4 20 Device control 4
NAK 21 Negative acknowledgement
SYN 22 Syncronize
ETB 23 End of transmission block
CAN 24 Cancel
EM 25 End of medium
SUB 26 Substitute
ESC 27 Escape - start of special sequence
FS 28 Form separator
GS 29 Group separator
RS 30 Record separator
US 31 Unit separator
Codes 00100000 to 01111110 (32 to 126 decimal are the
printable characters.
The printable characters are grouped in several sections.
Code 00100000 (32 decimal) is the space character.
Codes 00110000 to 00111001 (48 to 57 decimal) are the digit
characters '0' to '9'. The
character
'0' has ASCII code 48
When you type '0' on your keyboard, the computer receives a
binary 00110000 (48 decimal) from your terminal, not a
binary 0.
Codes 01000001 to 01011011 (65 to 71 decimal) are the
capital letters.
Codes 01100001 to 01111011 (97 to 123 decimal) are the lower
case letters. Note that the code for a lower case letter
differs by only 1 bit from the code for the same upper case
letter. This feature is intended to make it easy to
capitalize or decapitalize text.
Code 01111111 (127 decimal) is the delete character.
All remaining codes between the digits and letters are used
for various punctuation symbols.
ASCII Table
The following is a table of all 256 characters. The
appearance of non-standard characters 128 to 255
(third and fourth columns) will depend on the
type of terminal you are viewing this on. If your terminal
supports an alternate character set, it will be shown
following the standard character set.