# abcd.s -- a modular program in MIPS assembly (does the same thing
# as the C++ version abcd.C
# It would have been nice to name the procedures by single letters
# a, b, c and d, but unfortunately "b" is a reserved word.

	.data
str_a:		.asciiz "a"
str_b:		.asciiz "b"
str_c:		.asciiz "c"
str_d:		.asciiz "d"
newline:	.asciiz "\n"

	.text
main:
	jal proc_a		# call procedure proc_a
	
	li $v0, 4		# print newline
	la $a0, newline
	syscall

	jal proc_b		# call procedure proc_b

	li $v0, 4		# print newline
	la $a0, newline
	syscall

	jal proc_c		# call procedure proc_c

	li $v0, 4		# print newline
	la $a0, newline
	syscall

	jal proc_d		# call procedure proc_d

	li $v0, 4		# print newline
	la $a0, newline
	syscall

	li $v0, 10		# We're done!
	syscall

#-------------------------------------------------------------------
proc_a:
	li $v0, 4		# print the letter a
	la $a0, str_a
	syscall

	jr $ra			# return from procedure

#-------------------------------------------------------------------
proc_b:
	sw $ra, 0($sp)		# save return address
	addi $sp, $sp, -4

	jal proc_a		# call proc_a

	li $v0, 4		# print the letter b
	la $a0, str_b
	syscall

	addi $sp, $sp, 4	# restore return address
	lw $ra, 0($sp)

	jr $ra			# return from procedure

#-------------------------------------------------------------------
proc_c:
	sw $ra, 0($sp)		# save return address
	addi $sp, $sp, -4

	jal proc_a		# call proc_a
	jal proc_b		# call proc_b

	li $v0, 4		# print the letter c
	la $a0, str_c
	syscall

	addi $sp, $sp, 4	# restore return address
	lw $ra, 0($sp)

	jr $ra			# return from procedure

#-------------------------------------------------------------------
proc_d:
	sw $ra, 0($sp)		# save return address
	addi $sp, $sp, -4

	jal proc_a		# call proc_a
	jal proc_b		# call proc_b
	jal proc_c		# call proc_c

	li $v0, 4		# print the letter d
	la $a0, str_d
	syscall

	addi $sp, $sp, 4	# restore return address
	lw $ra, 0($sp)

	jr $ra			# return from procedure