Category : Word Processors
Archive   : COUNTLTR.ZIP
Filename : FREQ.ASM

.RHA.VA$FI/ p. .pn/ of .fp/

/.PT3/.AL1/.LM0/.RM80/
;----------------------------------------------------------------------
; freq.asm - count the letter frequency on the command line
; PC Magazine * PC Tutor
;----------------------------------------------------------------------
CSEG SEGMENT PARA PUBLIC 'CODE' ;Start CODE segment
ASSUME CS:CSEG,DS:CSEG,ES:CSEG,SS:CSEG ;Set by DOS Loader
ORG 100H ;COM file format

ENTPT: JMP MAIN

CR EQU 0DH
LF EQU 0AH

COPYRIGHT DB "FREQ 1.0 (c) Ziff Communications Co.",CR,LF
DB "PC Magazine ",254," Robert L. Hummel",CR,LF,"$",26

USAGE$ DB "Usage: FREQ text",CR,LF,"$"

ABC DB 26 DUP(0)

MAIN PROC NEAR

MOV DX,OFFSET COPYRIGHT
MOV AH,9
INT 21H

XOR CH,CH ;Zero high byte
MOV CL,DS:[80H] ;Get command line length
OR CL,CL ;If > 0
JNZ HAVE_INPUT ; count letters

MOV DX,OFFSET USAGE$ ;Address of message
MOV AH,9 ;Display string
INT 21H ; Thru DOS
MOV AX,4C01H ;Terminate with error
INT 21H ; Thru DOS
HAVE_INPUT:
MOV SI,81H ;Start of command tail
XOR BH,BH ;Zero high byte of index
READ_CHAR: LODSB ;Get character in AL
OR AL,20H ;Make lower case
SUB AL,"a" ;Convert to number
CMP AL,25
JA NEXT
MOV BL,AL ;Put into BL
INC BYTE PTR ABC[BX] ; to use as index
NEXT:
LOOP READ_CHAR ;Scan entire line

MOV SI,OFFSET ABC ;Offset of table
MOV CX,26 ;Number of entries
XOR BL,BL ;BL = 0
PR_CHAR:
MOV AH,2 ;Write TTY
MOV DL,CR ; carriage return
INT 21H ; thru DOS

MOV AH,2 ;Write TTY
MOV DL,LF ; line feed
INT 21H ; thru DOS

MOV DL,BL ;Build character in DL
INC BL ; move char counter
ADD DL,"A" ;Make ASCII value
MOV AH,2 ;Write TTY
INT 21H ; Thru DOS

MOV AH,2 ;Write TTY
MOV DL,20H ; a space
INT 21H ; Thru DOS

LODSB ;Get character count
CALL BYTE2DEC ;Print as decimal number

LOOP PR_CHAR ;Continue for entire table

MOV AX,4C00H ;Terminate program
INT 21H ;Thru DOS
MAIN ENDP

;======================================================================
; binary to decimal conversion. arguments 0 - 99 in AL
; Destroys AX, DL
;----------------------------------------------------------------------
BYTE2DEC PROC NEAR

XOR AH,AH
AAM
OR AX,"00" ;Make them ascii
PUSH AX
MOV DL,AH ; carriage return
MOV AH,2 ;Write TTY
INT 21H ; thru DOS
POP AX
MOV DL,AL
MOV AH,2
INT 21H
RET

BYTE2DEC ENDP

;-----------------------------------------------------------------------------

CSEG ENDS
END ENTPT