WeChat cstutorcs LC3 Prog1

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README.md

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+# LC3 Prog1
+
+# 程序代做代写 CS编程辅导
+
+# WeChat: cstutorcs
+
+# Email: tutorcs@163.com
+
+# CS Tutor
+
+# Code Help
+
+# Programming Help
+
+# Computer Science Tutor
+
+# QQ: 749389476

prog1.asm

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+WeChat: cstutorcs
+QQ: 749389476
+Email: tutorcs@163.com
+;
+; The code given to you here implements the histogram calculation that 
+; we developed in class.  In programming video lecture, we will discuss 
+;  how to prints a number in hexadecimal to the monitor.
+;
+; Your assignment for this program is to combine these two pieces of 
+; code to print the histogram to the monitor.
+;
+; If you finish your program, 
+;    ** Submit a working version to Gradescope  **
+
+
+
+	.ORIG	x3000		; starting address is x3000
+
+
+;
+; Count the occurrences of each letter (A to Z) in an ASCII string 
+; terminated by a NUL character.  Lower case and upper case should 
+; be counted together, and a count also kept of all non-alphabetic 
+; characters (not counting the terminal NUL).
+;
+; The string starts at x4000.
+;
+; The resulting histogram (which will NOT be initialized in advance) 
+; should be stored starting at x3F00, with the non-alphabetic count 
+; at x3F00, and the count for each letter in x3F01 (A) through x3F1A (Z).
+;
+; table of register use in this part of the code
+;    R0 holds a pointer to the histogram (x3F00)
+;    R1 holds a pointer to the current position in the string
+;       and as the loop count during histogram initialization
+;    R2 holds the current character being counted
+;       and is also used to point to the histogram entry
+;    R3 holds the additive inverse of ASCII '@' (xFFC0)
+;    R4 holds the difference between ASCII '@' and 'Z' (xFFE6)
+;    R5 holds the difference between ASCII '@' and '`' (xFFE0)
+;    R6 is used as a temporary register
+;
+
+	LD R0,HIST_ADDR      	; point R0 to the start of the histogram
+	
+	; fill the histogram with zeroes 
+	AND R6,R6,#0		; put a zero into R6
+	LD R1,NUM_BINS		; initialize loop count to 27
+	ADD R2,R0,#0		; copy start of histogram into R2
+
+	; loop to fill histogram starts here
+HFLOOP	STR R6,R2,#0		; write a zero into histogram
+	ADD R2,R2,#1		; point to next histogram entry
+	ADD R1,R1,#-1		; decrement loop count
+	BRp HFLOOP		; continue until loop count reaches zero
+
+	; initialize R1, R3, R4, and R5 from memory
+	LD R3,NEG_AT		; set R3 to additive inverse of ASCII '@'
+	LD R4,AT_MIN_Z		; set R4 to difference between ASCII '@' and 'Z'
+	LD R5,AT_MIN_BQ		; set R5 to difference between ASCII '@' and '`'
+	LD R1,STR_START		; point R1 to start of string
+
+	; the counting loop starts here
+COUNTLOOP
+	LDR R2,R1,#0		; read the next character from the string
+	BRz PRINT_HIST		; found the end of the string
+
+	ADD R2,R2,R3		; subtract '@' from the character
+	BRp AT_LEAST_A		; branch if > '@', i.e., >= 'A'
+NON_ALPHA
+	LDR R6,R0,#0		; load the non-alpha count
+	ADD R6,R6,#1		; add one to it
+	STR R6,R0,#0		; store the new non-alpha count
+	BRnzp GET_NEXT		; branch to end of conditional structure
+AT_LEAST_A
+	ADD R6,R2,R4		; compare with 'Z'
+	BRp MORE_THAN_Z         ; branch if > 'Z'
+
+; note that we no longer need the current character
+; so we can reuse R2 for the pointer to the correct
+; histogram entry for incrementing
+ALPHA	ADD R2,R2,R0		; point to correct histogram entry
+	LDR R6,R2,#0		; load the count
+	ADD R6,R6,#1		; add one to it
+	STR R6,R2,#0		; store the new count
+	BRnzp GET_NEXT		; branch to end of conditional structure
+
+; subtracting as below yields the original character minus '`'
+MORE_THAN_Z
+	ADD R2,R2,R5		; subtract '`' - '@' from the character
+	BRnz NON_ALPHA		; if <= '`', i.e., < 'a', go increment non-alpha
+	ADD R6,R2,R4		; compare with 'z'
+	BRnz ALPHA		; if <= 'z', go increment alpha count
+	BRnzp NON_ALPHA		; otherwise, go increment non-alpha
+
+GET_NEXT
+	ADD R1,R1,#1		; point to next character in string
+	BRnzp COUNTLOOP		; go to start of counting loop
+
+
+
+PRINT_HIST
+
+; you will need to insert your code to print the histogram here
+
+; do not forget to write a brief description of the approach/algorithm
+; for your implementation, list registers used in this part of the code,
+; and provide sufficient comments
+
+
+
+DONE	HALT			; done
+
+
+; the data needed by the program
+NUM_BINS	.FILL #27	; 27 loop iterations
+NEG_AT		.FILL xFFC0	; the additive inverse of ASCII '@'
+AT_MIN_Z	.FILL xFFE6	; the difference between ASCII '@' and 'Z'
+AT_MIN_BQ	.FILL xFFE0	; the difference between ASCII '@' and '`'
+HIST_ADDR	.FILL x3F00     ; histogram starting address
+STR_START	.FILL x4000	; string starting address
+
+; for testing, you can use the lines below to include the string in this
+; program...
+; STR_START	.FILL STRING	; string starting address
+; STRING		.STRINGZ "This is a test of the counting frequency code.  AbCd...WxYz."
+
+
+
+	; the directive below tells the assembler that the program is done
+	; (so do not write any code below it!)
+
+	.END