History of Basic
When timesharing computers first appeared there was a need for a language that could be used interactively by users and could be learned quickly.
BASIC (Beginner's All Purpose Symbolic Instruction Code) was written in 1963, at Dartmouth College, by John Kemeny and Tom Kurtzas.
Basic was developed to be an interpreted language. Up until that time users had to submit their programs as batch jobs on a mainframe computer, perhaps on punched cards, the punched cards had to be loaded, compiled, linked and run, the user would then get a printout with the results, perhaps several hours later.
With timesharing computers, users could type in their Basic program themselves, then type run and see the results instantly. Later when personal computers were invented Basic was a good way to allow people to start programming quickly on their own computer.
However Basic does have some bad points, it is not very scalable, it can encourage bad programming practices and interpreted programs can run slower. There are modern dialects of Basic which get round these problems by making the language more like a modern structured language but then you loose the simplicity.
If you are starting to learn programming from scratch it is far better to start with a modern language such as Java.
example of the original basic dialect:
10 READ A, B, C
20 LET R1 = (-B+(B^2 - 4*A*C)^0.5)/(2*A)
30 LET R2 = (-B-(B^2 - 4*A*C)^0.5)/(2*A)
40 PRINT "ROOTS OF EQUATION:"; R1 ; "AND" ; R2
50 DATA 2, -1, -1
60 END
RUN
ROOTS OF EQUATION: 1 AND -0.5
When the user types a line starting with a number, this is stored, when RUN is typed the stored code is then interpreted.
Dartmouth BASIC Language Elements
Declarations
| Examples | ||
| DIM | Declare upper bounds of array dimensions | 100 DIM A(20,20), B$(30) |
| DEF | Declare function | 100 DEF FNA(N)=N + SQR(N) |
Remark
| Examples | ||
| REM | Insert comment with source program listing | 100 REM PROCESS INPUT |
Assignment
| Examples | ||
| LET | Evaluate expression and assign value to variable | 100 LET A=B^2 - C |
Control statements
| Examples | ||
| GOTO | Unconditional branch | 100 GOTO 300 |
| IF ... THEN | Conditional branch | 100 IF A>B THEN 300 |
| ON | Indexed branch | 100 ON X-Y GOTO 300,400,500 |
| FOR .. STEP | Beginning of loop | 100 FOR N=1 TO 5 STEP 2 |
| NEXT | End of loop | 300 NEXT N |
| GOSUB | Subroutine call | 100 GOSUB 300 |
| RETURN | End of subroutine | 600 RETURN |
| STOP | Terminate program | 600 STOP |
| END | Halts execution | 9999 END |
Input/output statements
| Examples | ||
| READ | Assign values from data queue to specified variables | 100 READ A$,X |
| DATA | Establish values in data queue | 600 DATA FRED,10 |
| RESTORE | Return pointer to start of data queue | 600 RESTORE |
| INPUT | Assign values input from console to specified variables | 100 INPUT A$,X |
| Print specified values | 100 PRINT "RESULT+",A$,X |
Matrix operations
| Examples | ||
| MAT READ | Input values of whole matrix from data queue | 100 MAT READ A,B |
| MAT PRINT | Print whole matrix | 100 MAT PRINT A |
| MAT add/subtract | Add or subtract matrices | 100 MAT A = B + C - D |
| MAT multiply | Multiply matrix by matrix | 100 MAT A = B * C |
| MAT multiply by constant | Multiply matrix by constant | 100 MAT A = (2) * B |
| MAT INV | Invert matrix | 100 MAT A=INV(B) |
| MAT TRN | Transpose matrix | 100 MAT A=TRN(B) |
| MAT ZER | matrix with all zeros | 100 MAT A=ZER |
| MAT CON | matrix with all ones | 100 MAT A=CON |
| MAT IDN | identity matrix | 100 MAT A=IDN |
Commands
| Examples | ||
| BYE | exit from BASIC system | BYE |
| DELETE | delete lines from work file | DELETE 100-200 |
| LIST | complete or partial program listing | LIST 100-200 |
| NEW | setup scratch file as new work file | NEW fred |
| OLD | setup saved file as new work file | OLD fred |
| RENAME | rename work file | RENAME fred |
| RUN | cause program in work file to be executed | RUN |
| SAVE | copy work file to disc | SAVE |
| UNSAVE | delete saved program | UNSAVE fred |
Visual Basic
Microsoft have modified the language to include Object Oriented capabilities (but taken out the built in matrix types!)
