Instructions
Objective
Write a program to find prime numbers up to value and guess the number in ARM assembly for Raspberry Pi.
Requirements and Specifications
Do two programs. You should do either 1 or 2, and then either 3 or 4. Note that all the programs require 2 loops and an if test, so to my mind the 1 and 2 are equivalent, and 3 and 4 are equivalent.
- Write a program to find prime numbers from 3 to n in a loop by dividing the number n by all numbers from 2..n/2 in an inner loop. Using the remainder (rem) operation, determine if n is divisible by any number. If n is divisible, leave the inner loop. If the limit of n/2 is reached and the inner loop has not been exited, the number is prime and you should output the number. So if the user were to enter 25, your program would print out "2, 3, 5, 7, 11, 13, 17, 19, 23".
- Write a program to prompt the user for a number, and determine if that number is prime. Your program should print out "Number n is prime" if the number is prime, and "Number n is not prime if the number is not prime. The user should be able to enter a "-1" to end the problem. It should print an error if 0, 1, 2 or any negative number other than -1 are entered.
- Write a program to allow a user to guess a random number generated by the computer from 1 to maximum (the user should enter the maximum value to guess). In this program the user will enter the value of maximum. The user will then enter guesses and the program should print out if the guess is too high or too low until the user guesses the correct number. The program should print out the number of guesses the user took.
- Write a program to guess a number chosen by the user. In this program a user will choose a secret number from 1..maximum. The program will prompt the user for the maximum value, which the user will enter. The program will then make a guess as to the value of the secret number, and prompt the user to say if the actual number is higher, lower, or correct. The computer will then guess another number until it guesses the correct secret number. The program should use a binary search to narrow its guesses to select its next guess after each attempt.
Screenshots of output
Source Code
Program 1
.data
title: .asciz "This program finds the primes between 2 and n.\n\n"
prompt: .asciz "Please enter the number n: "
format: .asciz "%d"
comma: .asciz ", "
newline: .asciz "\n"
n: .space 4
.text
.global main
main:
sub sp, sp, #4 @ save return address
str lr, [sp]
@ print program title
ldr r0, =title @ load address of title message
bl printf @ print the title
@ print prompt
ldr r0, =prompt @ load address of prompt
bl printf @ print the prompt
@ read number
ldr r0, =format @ load address of number format
ldr r1, =n @ load address of variable to save read number
bl scanf @ read number
ldr r0, =n @ load address of number
ldr r4, [r0] @ load number
@ calculate primes
mov r6, #2 @ start in 2
loop1:
cmp r6, r4 @ see if we reached n
bgt endloop1 @ if so, end
lsr r5, r6, #1 @ calculate n / 2
mov r7, #2 @ start divisor in 2
loop2:
cmp r7, r5 @ compare wit n/2
bgt prime @ if we reached n/2, is a prime
mov r0, r6 @ load current number
mov r1, r7 @ load divisor
bl __aeabi_uidivmod @ divide and get remainder in r1
cmp r1, #0 @ see if remainder is zero
beq nextnum @ if it's divisible by the current divisor, is not a prime
add r7, r7, #1 @ increment divisor
b loop2 @ repeat inner loop
prime:
cmp r6, #2 @ see if it's 2
beq printnum @ if so, don't print comma
ldr r0, =comma @ load format to print a comma
bl printf @ print comma
printnum:
ldr r0, =format @ load format to print a number
mov r1, r6 @ load number
bl printf @ print the number
nextnum:
add r6, r6, #1 @ advance to next number
b loop1 @ repeat outer loop
endloop1:
@ print a newline
ldr r0, =newline @ load format to print a comma
bl printf @ print comma
ldr lr, [sp] @ restore return address
add sp, sp, #4
bx lr @ return to os
Program 2
.data
title: .asciz "This program guesses a number chosen by the user from 1..maximum.\n"
prompt1: .asciz "\nChoose a number and enter the maximum (-1 to exit): "
prompt2: .asciz "Is your number %d (Y = correct, L = lower, H = higher)?: "
error: .asciz "Please enter Y for correct, L for lower or H for higher.\n"
result: .asciz "The number was found in %d guesses\n"
format: .asciz "%d"
n: .space 4
.text
.global main
main:
sub sp, sp, #4 @ save return address
str lr, [sp]
@ print program title
ldr r0, =title @ load address of title message
bl printf @ print the title
loop1:
@ print prompt for maximum
ldr r0, =prompt1 @ load address of prompt
bl printf @ print the prompt
@ read number
ldr r0, =format @ load address of number format
ldr r1, =n @ load address of variable to save read number
bl scanf @ read number
bl getchar @ read ending enter
mov r4, #1 @ minimum
ldr r0, =n @ load address of number
ldr r5, [r0] @ load maximum number
cmp r5, #0 @ compare with zero
ble endloop1 @ if <=0, end loop
mov r7, #0 @ number of guesses = 0
@ guess number
loop2:
add r6, r4, r5 @ min + max
lsr r6, r6, #1 @ calculate mid
add r7, r7, #1 @ increment guesses
readval:
@ print guess and ask to validate it
ldr r0, =prompt2 @ load address of prompt
mov r1, r6 @ copy current guess
bl printf @ print the prompt
@ read validation
bl getchar
mov r8, r0
bl getchar @ read ending enter
cmp r8, #'y' @ if correct
beq found
cmp r8, #'Y' @ if correct
beq found
cmp r8, #'l' @ if it's lower
beq lower
cmp r8, #'L' @ if it's lower
beq lower
cmp r8, #'h' @ if it's higher
beq higher
cmp r8, #'H' @ if it's higher
beq higher
@ else print error message
ldr r0, =error @ load address of error message
bl printf @ print the message
b readval @ read again
lower:
sub r5, r6, #1 @ use mid - 1 as max
b loop2 @ repeat loop
higher:
add r4, r6, #1 @ use mid + 1 as min
b loop2 @ repeat loop
found:
ldr r0, =result @ load format to print result
mov r1, r7 @ load number of guesses
bl printf @ print the result
b loop1 @ read another max
endloop1:
ldr lr, [sp] @ restore return address
add sp, sp, #4
bx lr @ return to os