Apple II manual This is Probably the Most Important Speed Hint, Old Aim

2.THIS IS PROBABLY THE MOST IMPORTANT SPEED HINT.

Use variables instead of constants. It takes more time to convert a constant to its floating point representation than it does to fetch the value of a simple or matrix variable. This is especially important within FOR...NEXT loops or other code that is executed repeatedly.

3.Variables which are encountered first during the execution of a BASIC program are allocated at the start of the variable table. This means that a statement such as 5 A=0:B=A:C=A, will place A first, B second, and C third in the symbol table (assuming line 5 is the first statement executed in the program). Later in the program, when BASIC finds a reference to the variable A, it will search only one entry in the symbol table to find A, two entries to find B and three entries to find C, etc.

4.Use NEXT statements without the index variable. NEXT is somewhat faster than NEXT I because no check is made to see whether the variable specified in the NEXT is the same as the variable in the most recent FOR statement.

D CONVERTING BASIC PROGRAMS NOT WRITTEN FOR AIM 65 BASIC

Though implementations of BASIC on different computers are in many ways similar, there are some incompatibilities which you should watch for if you are planning to convert some BASIC programs that were not written in AIM 65 BASIC.

1.Matrix subscripts. Some BASICs use "[" and "]" to denote matrix subscripts. AIM 65 BASIC uses "(" and ")".

2.Strings. A number of BASICs force you to dimension (declare) the length of strings before you use them. You should remove all dimension statements of this type from the program. In some of these BASICs, a declaration of the form DIM A$(I,J) declares a string matrix of J elements each of which has a length I. Convert DIM statements of this type to equivalent ones in AIM 65 BASIC: DIM A$(J).

AIM 65 BASIC uses "+" for string concatenation, not "," or "&".

AIM 65	BASIC uses LEFT$, RIGHT$			and	MID$ to take	substrings	of strings. Other
BASICs	uses A$(I) to	access	the	Ith	character of	the string	A$, and A$(I,J) to	take a
substring of A$ from		character position I to character position J. Convert as follows:
OLD		AIM	65

A$(I)MID$(A$,I,1)

A$(I,J)MID$(A$,I,J-I+1)

This assumes that the reference to a substring of A$ is in an expression or is on the right side of an assignment. If the reference to A$ is on the left hand side of an assignment, and X$ is the string expression used to replace characters in A$, convert as follows:

OLD AIM 65

A$(I)=X$A$=LEFT$(A$,I-1)+X$+MID$(A$,I+1)

A$(I,J)=X$A$=LEFT$(A$,I-1)+X$+MID$(A$,J+1)

3.Multiple assignments. Some BASICs allow statements of the form: 500 LET B=C=0. This statement would set the variables B & C to zero.

In AIM 65 BASIC this has an entirely different effect. All the "='s" to the right of the first one would be interpreted as logical comparison operators. This would set the variable B to -1 if C equaled 0. If C did not equal 0, B would be set to 0. The easiest way to convert statements like this one is to rewrite them as follows:

500C=0:B=C

4.Some BASICs use "/" instead of ":" to delimit multiple statements per line. Change all occurrences of "/" to ":" in the program.