Language characteristics
In common with many early implementations of BASIC, SOBS needed lines to haveGOTO and GOSUB statements. A RENUMBER facility was available to allow for sections of the code to be renumbered, by default in increments of 10, to allow more space in the middle of a program.
Other than line numbers, all numeric values were represented internally as Statements
The language had relatively few statements by comparison with modern programming languages: Note in particular the lack of aWHILE-like statement; FOR was the only looping construct available to programmers.
Variables
Variable names for numeric values were either a single letter, or a single letter followed by a single numeric digit, thus allowing for 286 discreet variables in total. Strings were supported; variable names for them had the same restriction but were followed by a pound (£) symbol.
Functions
A limited number of numeric functions were provided, all of which took one numeric parameter: Support for strings was more limited, with only one function,LEN, which returned the length of the string parameter. Sub-strings were supported with square brackets, so A£ ,3/code> referred to the sub-string of the string A£ from the 2nd character to the 3rd character inclusive, so
10 LET A£ = "FOO"
20 PRINT A£ ,3
would print OO
This syntax was also supported on the left-hand side of an assignment, so
10 LET A£ = "FOO"
20 LET A£ ,2= "BAR"
30 PRINT A£
would print FBARO
Arrays
Support for handling arrays of data was relatively strong, with MAT statements able to read an entire array from DATA statements, and perform useful matrix
Matrix (: matrices or matrixes) or MATRIX may refer to:
Science and mathematics
* Matrix (mathematics), a rectangular array of numbers, symbols or expressions
* Matrix (logic), part of a formula in prenex normal form
* Matrix (biology), the m ...
operations such as matrix addition
In mathematics, matrix addition is the operation of adding two matrices by adding the corresponding entries together.
For a vector, \vec\!, adding two matrices would have the geometric effect of applying each matrix transformation separately ...
, matrix subtraction
In mathematics, matrix addition is the operation of adding two matrices by adding the corresponding entries together.
For a vector, \vec\!, adding two matrices would have the geometric effect of applying each matrix transformation separately on ...
, matrix multiplication
In mathematics, specifically in linear algebra, matrix multiplication is a binary operation that produces a matrix (mathematics), matrix from two matrices. For matrix multiplication, the number of columns in the first matrix must be equal to the n ...
, and finding the inverse matrix
In linear algebra, an invertible matrix (''non-singular'', ''non-degenarate'' or ''regular'') is a square matrix that has an inverse. In other words, if some other matrix is multiplied by the invertible matrix, the result can be multiplied by an ...
for a square matrix
In mathematics, a square matrix is a Matrix (mathematics), matrix with the same number of rows and columns. An ''n''-by-''n'' matrix is known as a square matrix of order Any two square matrices of the same order can be added and multiplied.
Squ ...
.
Example:
10 DIM A(3,3)
20 MAT READ A
30 DATA 1,1,2,1,0,2,0,2,1
40 DIM B(3,3)
50 MAT READ B
60 DATA 0,0,1,0,1,0,1,0,0
70 DIM C(3,3),D(3,3)
80 MAT C=A*B
90 MAT D=INV(C)
100 MAT PRINT D,
The output would be
2 2 1
1 -1 0
4 -3 -2
Debugging
SOBS had primitive debugging capabilities, limited mostly to the TRACE statement. TRACE ON would cause the interpreter to print each line number as it was executed.
References
{{DEFAULTSORT:Southampton Basic System
BASIC interpreters
ICL programming languages
Science and technology in Hampshire
University of Southampton
BASIC programming language family