CESIL

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CESIL, or Computer Education in Schools Instruction Language, [1] is a programming language designed to introduce pupils in British secondary schools to elementary computer programming. It is a simple language containing a total of fourteen instructions.

Contents

Background

Computer Education in Schools (CES) was a project developed in the late 1960s and early 1970s by International Computers Limited (ICL). [2] CESIL was developed by ICL as part of the CES project, and introduced in 1974. [3] In those days, very few if any schools had computers, so pupils would write programs on coding sheets, which would then be transferred to punched cards or paper tape. [4] Typically, this would be sent to run on a mainframe computer, with the output from a line printer being returned later. [5]

Structure

Because CESIL was not designed as an interactive language, there is no facility to input data in real time. Instead, numeric data is included as a separate section at the end of the program. [6]

The fundamental principle of CESIL is the use of a single accumulator, which handles mathematical operations. [4] Numeric values are stored in variables, which in CESIL are referred to as store locations. [7] CESIL only works with integers, and results from DIVIDE operations are rounded if necessary. [8] There is no facility for data structures such as arrays, nor for string handling, though string constants can be output by means of the PRINT instruction. [4]

Jumps and loops can be conditional or non-conditional, and transfer operation of the program to a line with a specific label, which is identified in the first column of a coding sheet. [9] The instruction or operation is stated in the second column, and the operand in the third column. [10] On some coding sheets, comments and the text of the PRINT instruction would be written in a fourth column. [11]

Instructions

Instructions, or operations, are written in upper case and may have a single operand, which can be a store location, constant integer value or line label. Store locations and line labels are alphanumeric, up to six characters, and begin with a letter. [12] Numeric integer constants must be signed + or −, with zero being denoted as +0. [13] [lower-alpha 1]

Input and output

Memory storage

Mathematical instructions

In each case, the result of the operation is stored in the accumulator, replacing the previous value.

Program control

Other symbols

Three special symbols are used in CESIL at the beginnings of lines.

CESIL programming tools

An emulator for CESIL, designed to run on Windows and called Visual CESIL, is available as freeware. [27]

An interpreter for CESIL, designed to run on the Android platform and called Wyrm CESIL, is available as free to install. [28]

Example

The following totals the integers in the runtime data section until it encounters a negative value and prints the total.

        LOAD    +0 LOOP    STORE   TOTAL         IN         JINEG   DONE         ADD     TOTAL         JUMP    LOOP  DONE    PRINT   "The total is: "         LOAD    TOTAL         OUT         LINE         HALT  % 1 2 3 -1 *

The output of the above program would be:

The total is: 6

See also

Bibliography

Monsoon, Colin C; Sewell, Ian R; Frances P, Vickers (1978). Computer Studies. Vol. Book 1. ICL Computer Education in Schools. ISBN   0-903885-17-4.

Notes

  1. ↑ Visual CESIL does not require non-negative constants to be signed.
  2. ↑ Not supported in Visual CESIL. * is used instead.

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References

  1. ↑ Computer Studies, page 71
  2. ↑ "ICL–CES: Computer Education in Schools". Archived from the original on 19 June 2021. Retrieved 16 June 2021.
  3. ↑ Furber, Steve (January 2012). "Appendix J: Timeline of major developments in Computing in schools in England". Shut down or restart? The way forward for computing in UK schools (PDF). The Royal Society. p. 120. Archived (PDF) from the original on 2021-05-06. Retrieved 20 June 2021.
  4. 1 2 3 4 Computer Studies, page 72
  5. ↑ "My First Program". Archived from the original on 24 June 2021. Retrieved 16 June 2021.
  6. ↑ Computer Studies, page 82
  7. ↑ Computer Studies, page 76
  8. 1 2 Computer Studies, pages 93–94
  9. 1 2 Computer Studies, page 148
  10. 1 2 Computer Studies, page 77
  11. 1 2 Computer Studies, page 74
  12. ↑ Computer Studies, pages 96, 148
  13. ↑ Computer Studies, pages 97–99
  14. ↑ Computer Studies, page 201
  15. 1 2 3 Computer Studies, page 73
  16. ↑ Computer Studies, pages 199–200
  17. ↑ Computer Studies, pages 80, 97–98
  18. ↑ Computer Studies, pages 84, 97–98
  19. ↑ Computer Studies, pages 86, 97–98
  20. ↑ Computer Studies, pages 90, 97–98
  21. ↑ Computer Studies, pages 92, 97–98
  22. ↑ Computer Studies, page 145
  23. ↑ Computer Studies, page 198
  24. ↑ Computer Studies, page 154
  25. ↑ Computer Studies, page 83
  26. ↑ Computer Studies, page 164
  27. ↑ Andrew John Jacobs (20 June 2010). "Visual CESIL". Archived from the original on 12 September 2021. Retrieved 26 November 2021.
  28. ↑ Wyrm Software (13 October 2019). "Wyrm CESIL". Archived from the original on 25 November 2021. Retrieved 25 November 2021.
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