CESIL

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]

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, 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]

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]

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

• Computer literacy
• Computers in the classroom
• History of computer science

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.