| We have seen, in the History of the Computer | | | | was punched in the tape so that it could be |
| series, how machine code is used to operate a | | | | moved through the reader.As we know from our |
| computer so that it can use 1s and 0s to | | | | look at binary codes, 5 bits will give us a |
| interpret a program's intentions. But what | | | | total of 31 characters (1+2+4+8+16) plus |
| about a code for human communication with the | | | | zero. With 26 being used for the English |
| computer? We can variously write and read to | | | | alphabet, the other characters are used for |
| and from different media, such as paper tape, | | | | Carriage Return, Line Feed, etc. These are |
| magnetic tape, disk or teletype, but we need | | | | needed to operate the typewriter used to |
| some means of converting English (or another | | | | print out the information. Another character, |
| language) into a form which can be carried on | | | | Bel was used to ring a bell on the typewriter |
| these media.You may recall the old Western | | | | to alert the operator.Later a Shift character |
| movies where the James gang shoot the | | | | was incorporated, similar to the Shift key on |
| telegraph operator so he can't call the | | | | a typewriter, so that following characters |
| Marshall for help. Or the movies about the | | | | would indicate numbers. Another shift code |
| '29 Wall St crash where the tycoon reads the | | | | would switch back to letters. This Baudot |
| bad news on the ticker tape and promptly | | | | Code was used on teletype machines to |
| leaps out of 32nd floor window. Both of | | | | transmit data from one location to another. |
| these are early examples of a code being used | | | | This was later accomplished by first punching |
| on a medium. In this case morse code on the | | | | the tape, and then transmitting it by feeding |
| telegraph, and an analog code produced from a | | | | it through a 'high speed' reader. These |
| keyboard at the transmitting point, also sent | | | | speeds were gradually increased as the |
| by telegraph. The ticker tape, so called | | | | technology improved, and were generally |
| because of the noise made by the printing | | | | expressed as the 'Baud Rate', roughly |
| mechanism, carried the Stock Code, as used in | | | | equivalent to bits per second, also named |
| today's stock market, and a quote.A later | | | | after Baudot. Most problems came from |
| code used for paper tape, the baudot code, | | | | punching errors and synchronising transmitter |
| named after the French inventor, Baudot, was | | | | and receiver.In part 2 we look at how codes |
| a five bit code, punched across the tape, | | | | are used in computers.Tony is an experienced |
| giving a 1s and 0s pattern to make up the 26 | | | | computer engineer. He is currently webmaster |
| letters of the alphabet. The tape was an inch | | | | and contributor to . A set of diagrams |
| wide and came on big reels. A sprocket hole | | | | accompanying these articles may be seen at . |