Introduction to Data Communications
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22b. ASCII - American Standard Code for Information Interchange

ASCII is the most popular code and is used by the majority of the computing world. ASCII itself is a 7 bit code which allows only 128 characters (27). Most applications follow IBM's Extended ASCII code which uses 8 bits and allows an addition 128 graphic characters for a total of 256 characters (28). We will be concentrating on 7 bit ASCII codes.

Format effectors

Format effectors control the movement of the cursor on the screen and the print head in a printer. The format effectors are:

BSBackspace
HTHorizontal Tab
LFLine Feed
CRCarriage Return
FFForm Feed
VTVertical Tab

Communication Controls

Communication Controls are used in controlling data transmission over a communication network. They are used in both Asynchronous and Synchronous Transmissions. They are used in "handshaking".

STX Start of Text
ETXEnd of Text
EOT End of Transmission
ENQEnd of Inquiry
ACK Acknowledge
NAK Negative Acknowledge
EXTInterrupt
SYNSynchronous idle
ETB End of Block
EOFEnd of File

Information Separators

Information separators are used to separate database enquiries and files:

FS File Separator (in a PC - used as cursor R, L, U, D)
GS Group Separator
RS Record Separator
US Unit Separator

Introduction to Data Communications
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