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To convert an angle measured in degrees to radians. 1 radian equals approximately 57 degrees.
A function converting an angular argument given in degrees to radian measure.
To enable numbers or words that are required in a program to be made available every time the program is run. It does this by reading numbers or words into numeric or string variables from DATA statements in the program. Most often the data is read into an array. See the keyword DIM on page 120 for more information on arrays.
See the keyword DATA on page 227 for a more detailed description.
100 READ name$(X),A
A statement which copies the next item from a data-list into the variable or variables which follow the keyword READ. The DATA must contain the correct sequence of string and numeric data for the string and numeric variables to be assigned. In other words numeric data must be supplied if a numeric variable is to be filled.
200 INPUT "How many pounds can you afford" ,AFFORD
210 PRINT "You can afford the following cars"
220 FOR X=1 TO 10
230 READ NAME$
240 READ PRICE
250 IF PRICE < AFFORD THEN PRINT NAME$
500 REM British Leyland Cars
510 DATA METRO HLE,3695
520 DATA etc etc
To enable the program writer to put remarks and comments into the program to help him remember what the various parts of the program do. The computer completely ignores anything that appears after a REM.
When you first start writing small programs you can get away with having no REMs, but as your programs grow in complexity you will find it quite essential to have them liberally sprinkled over your program. If you come back to a program six months after you wrote it and find no REMs you will have a real job trying to remember how it worked and why you used that variable name etc. etc. Use lots of REMs - it will save you hours of time in the long run.
10 REM this revision dated 25-3-82
550 REM data for British Leyland cars
This statement allows comments to be inserted in a program.
When you type in a program you give each instruction a line number. As the program develops you quite often have to insert extra lines between other lines. You might well need to insert 25 lines between line number 300 and 310 - difficult!
The RENUMBER command will go through your program and renumber it automatically. It deals successfully with things like GOTO 220 - which might well become GOTO 180 etc. However if your program contains the statement GOTO 100 and there is no line 100 then the RENUMBER command will be unable to deal with the problem. and will say
Failed at line....
If you renumber a program containing an ON GOTO statement which contains a calculated line number, e.g.
ON X GOTO 120,240,2*R,1000,2000
then RENUMBER will deal successfully with references before the calculated line number. However it will not deal with the calculated line number or other line numbers in the same statement - ie 2*R, 1000 and 2000 in the example given.
The command RENUMBER will renumber your program giving the first line the number 10, the second 20 and so on.
The command RENUMBER 200 will give the first line of your program the number 200, the second will become line 210 etc. etc.
The command RENUMBER 200,4 would renumber starting with line 200 and then using 204,208 etc. etc.
RENUMBER is a command: it cannot be used in a program, or as part of a multiple statement line.
RENUMBER is a command which renumbers a user's program and will correct most of the cross-references within the program.
To make the computer repeat a set of instructions a number of times until some condition is met.
If you jump out of a REPEAT...UNTIL loop with a GOTO statement (which is bad practice) you must jump back in.
A single REPEAT may have more than one UNTIL.
10 REM print stars for 1 second
30 REPEAT PRINT "*";
40 UNTIL TIME=NOW+100
A statement which is the start of a REPEAT...UNTIL loop.
These loops always execute once and may be nested up to a depth of 20.
To get the computer to report in words what the last error was.
REPORT prints the error message appropriate to the last error condition.
ERR, ERL, ON ERROR
Sometimes it is useful to have several sets of data in one program. For example one might want information on British Leyland cars and on Lotus cars as in the example shown on page 128. The RESTORE statement enables the data-pointer to be moved from one set of data to the other.
The word RESTORE by itself resets the data pointer to the first set of data in the program.
100 RESTORE 6500
This statement can be used at any time to reset the data pointer to any selected line number.
The word RETURN - not the key marked RETURN - is used in a program at the end of a subroutine to make the computer return to the place in the program which originally 'called' the subroutine. See GOSUB on page 265 for more details.
There may be more than one RETURN statement in a subroutine - but preferably there should be one entry point and one (RETURN) exit point.
You should try very hard to avoid leaving a subroutine with GOTO, you should always exit with RETURN. Why? Well you will soon discover in reasonable sized programs that you can get into an awful tangle and lose track of how a program works if you make the program jump all over the place.
The importance of dividing your programs into clearly defined sections wherever possible, with one entry point and one exit point, cannot be over emphasised.
300 IF X>4 THEN RETURN
A statement which causes the program to branch to the statement after the one which contained the GOSUB which called the current subroutine.
GOSUB, ON GOSUB
To copy the right hand part of one string into another string. For example if
ABCDE$="HOW ARE YOU" then
RIGHT$(ABCDE$,3) would be "YOU" and
RIGHT$(ABCDE$,7) would be "ARE YOU"
Note that RIGHT$(ABCDE$,100) would be "HOW ARE YOU" since there are only eleven characters in HOW ARE YOU.
A string function returning a specified number of characters from the right hand end of another string.
To generate, or make, a random number.
What exactly this function does is determined by the number which follows the word RND.
RND by itself generates a random whole number between -2147483648 and 2147483647
RND(-X) returns the value -X and resets the random number generator to a number based on X
RND(0) repeats the last random number given by RND(1)
RND(1) generates a random number between 0 and 0.999999
RND(X) generates a random whole number between (and possibly including) 1 and X
The brackets are compulsory and must immediately follow the word RND with no intervening space.
950 PRINT RND(1)
A function generating a random number. The range of the number generated depends on the argument (if any).
To make the computer obey the statements in the program in its memory.
All variables (except the resident integer numeric variables @% and A% to Z%) are first deleted and then the program is executed.
RUN is a statement and programs may therefore execute themselves.
If you want to start a program without clearing all the variables then you can use the statement
or GOTO whatever line number you wish to start from, instead of RUN.
RUN is a statement causing the computer to execute the current program.
NEW, OLD, LIST, CHAIN