Arrays: Difference between revisions
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* [[Collections]]
* [[Two-dimensional array (runtime)]]
=={{header|8051 Assembly}}==
There are three types of fixed-length arrays:<ul>
<li>In the code segment - array elements are constant; good for strings, elements are easily indexed
<li>In internal RAM - good for small arrays; elements are easily indexed
<li>In external RAM - element retrieval/altering is most efficiently done sequentially, necessary for large arrays or peripherals</ul>
Dynamic (resizable) arrays are possible to implement, but are error-prone since bounds checking must be done by the programmer.
<lang asm>; constant array (elements are unchangeable) - the array is stored in the CODE segment
myarray db 'Array' ; db = define bytes - initializes 5 bytes with values 41, 72, 72, etc. (the ascii characters A,r,r,a,y)
myarray2 dw 'A','r','r','a','y' ; dw = define words - initializes 5 words (1 word = 2 bytes) with values 41 00 , 72 00, 72 00, etc.
; how to read index a of the array
push acc
push dph
push dpl
mov dpl,#low(myarray) ; location of array
mov dph,#high(myarray)
movc a,@a+dptr ; a = element a
mov r0, a ; r0 = element a
pop dpl
pop dph
pop acc ; a = original index again
; array stored in internal RAM (A_START is the first register of the array, A_END is the last)
; initalise array data (with 0's)
push 0
mov r0, #A_START
clear:
mov @r0, #0
inc r0
cjne r0, #A_END, clear
pop 0
; how to read index r1 of array
push psw
mov a, #A_START
add a, r1 ; a = memory location of element r1
push 0
mov r0, a
mov a, @r0 ; a = element r1
pop 0
pop psw
; how to write value of acc into index r1 of array
push psw
push 0
push acc
mov a, #A_START
add a, r1
mov r0, a
pop acc
mov @r0, a ; element r1 = a
pop 0
pop psw
; array stored in external RAM (A_START is the first memory location of the array, LEN is the length)
; initalise array data (with 0's)
push dph
push dpl
push acc
push 0
mov dptr, #A_START
clr a
mov r0, #LEN
clear:
movx @dptr, a
inc dptr
djnz r0, clear
pop 0
pop acc
pop dpl
pop dph
; how to read index r1 of array
push dph
push dpl
push 0
mov dptr, #A_START-1
mov r0, r1
inc r0
loop:
inc dptr
djnz r0, loop
movx a, @dptr ; a = element r1
pop 0
pop dpl
pop dph
; how to write value of acc into index r1 of array
push dph
push dpl
push 0
mov dptr, #A_START-1
mov r0, r1
inc r0
loop:
inc dptr
djnz r0, loop
movx @dptr, a ; element r1 = a
pop 0
pop dpl
pop dph
</lang>
=={{header|ACL2}}==
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