CESIL: Ранний учебный язык программирования для школ.

Educational computer programming language

CESIL, or Computer Education in Schools Instruction Language, 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.

Computer Education in Schools (CES) was a project developed in the late 1960s and early 1970s by International Computers Limited (ICL). CESIL was developed by ICL as part of the CES project, and introduced in 1974. 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. Typically, this would be sent to run on a mainframe computer, with the output from a line printer being returned later.

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. The fundamental principle of CESIL is the use of a single accumulator, which handles mathematical operations. CESIL only works with integers, and results from DIVIDE operations are rounded if necessary. 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. The instruction or operation is stated in the second column, and the operand in the third column. On some coding sheets, comments and the text of the PRINT instruction would be written in a fourth column.

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. Numeric integer constants must be signed + or −, with zero being denoted as +0.

IN – reads the next value from the data, and stores it in the accumulator. OUT – prints the current value of the accumulator. No carriage return is printed. PRINT "text in quotes" – prints the given text. No carriage return is printed.

LOAD location or LOAD constant – copies the value of the given location or constant to the accumulator. STORE location – copies the contents of the accumulator to the given location. SUBTRACT location or SUBTRACT constant – subtracts the value of the given location or constant from the accumulator. MULTIPLY location or MULTIPLY constant – multiplies the accumulator by the value of the given location or constant. DIVIDE location or DIVIDE constant – divides the accumulator by the value of the given location or constant. The result is rounded down if the result is positive, and up if the result is negative. In each case, the result of the operation is stored in the accumulator, replacing the previous value.

JUMP label – unconditionally transfers control to location labelled. JINEG label (Jump If NEGative) – transfers control to location labelled if the accumulator contains a negative value. JIZERO label (Jump If ZERO) – transfers control to location labelled if the accumulator contains zero. ( is used at the start of a line to indicate a comment.

An emulator for CESIL, designed to run on Windows and called Visual CESIL, is available as freeware. An interpreter for CESIL, designed to run on the Android platform and called Wyrm CESIL, is available as free to install.