May June 1980 - Commodore Computers

MAY/JUNE. I 198O. 1980. ISSUE 4. COMPUTE. 77 n
PETGETWITH
FLASHING
CURSOR
Gary Greenberg
35-63 SOth St.
Jackson Hts., , NY 11372
There are many reasons why some programmers
prefer to use the GET statement for keyboard input
rather than the INPUT statement. ent. One reason of
interest to many beginners is that the ,he GET statement
can help prevent falling out of the program
when the wrong response is made. For example,
pressing RETURN as a response to INPUT causes
you to fall out of the program. Similarly if you
call for a numeric variable and type an alphabetic
character, again you are in trouble.
The GET statementt works by checking the keyboard
input buffer for the next character. However, H without the benefit of appropriate software routines,
the GET statement collects only one character, does
not provide a cursor for a prompt, does not print
the character on the screen and does not permit you
to erase the result before entering 'he the data.
Additionally, the statement is executed so rapidly
you will probably not be able to enter it in time to
get it accepted. You do not use a carriage return
to signal the end of the entry.
A number of magazines have provided software
pieces to enable you to use the GET but they do
not permit you to delete and correct the entry before
entering it into the program. The following program
permits you to use the GET statement instead of the
INPUT statement. It will permit you to have a
flashing cursor and it will permit you to delete
and correct entries before committing them to the
computer. You use the carriage return to signal the
end of your entry. You will not fall out of your
program if you respond with a carriage return.
program if you respond with a carriage return.
Program Listing
Program Listing
100 PRINT'WHAT " IS ANSWER?";:GOSUB A 1000
110 PRINTZ1$:Z1 PRINTZIS,ZI = ~ VAL(ZI$),PRINTZI
VAL{Z1S):PRINTZ1
1000 REM GET WITH FLASHING CURSOR
1010 ZS . ····,ZIS = ....
1010 ZS -"":Z1| =""
1020 IU2U PRINT"R ' R rd" rcl";:FORI :: FOIU 0: = I TTOO 35:NEXTI
Gary Greenberg
35-63 80th St.
1030 PRINT"cl";:FORI I'RI Nr 'd " "FORI = - I 1 ·f TOO 35,NEXT 35:NEXTII
1040 [040GETZ$:IFZS=""THEN1020
GETZS, = .... TH EN 1020
1050 REM ERASE ENTRY CHECK
1060 IFZS IFZ$ < > CHR$(20)THEN HRS(20)THEN 1110
10
1070 IF2I-""THEN I FZS •.. " EN 1020
1080 ZZ . =LEN(Z1$):IF LEN(ZIS), IF ZZ < I 1 THEN 1020
1090 ZIS-LEFTS(Zl$,ZZ-l|:PRINT"d";
= I S.ZZ- I ), I' ·· d ··:
1100 GOTO 1020
1110 IFZS =CHRS(13) OR ZS Z$ =CHRS(141) THEN 1150
1120 PRINT ZS Z$; ,
1130ZIS Z1$=Z1$+Z$ · ZIS + ZS
1140 GOTO 1020
1150 GETZ8:IF ZS, ZS Z$ ~ -- ····THEN ""THEN 1150
50
1160 RETURN
The program is a subroutine that can be called in
place of any INPUT statements. Here's how it works_
works.
LINE 100: The print message is used as a prompt.
GET does not provide a question mark and you will
have to put it into the PRINT statement if you
want it. After the prompt is printed the program
jumps to the subroutine,
subroutine.
LINE 110: This line is the line after the subroutine
is executed. You can use any program statements you
wanl. want. The one here is just an illustration. The PRINT
Z Zl$ 1 $ is redundant since it is printed out in the subroutine.
The VAL statement is used to convert the
STRING to a NUMERIC. You should note that the
subroutine leaves the cursor immediately after the
entry. If you want a linefeed you will have to
insert a I"PRINT:" I I' in line 110.
LINE 1000: The subroutine starts here.
LINE 1010: 10: Z$ will be used to collect the data
typed in. ZI$ Zl$ will be used to build a string out of
the data entered. This line initializes both strings
as Nulls s (empty).
LINES 1020-10.30: 1020-1030: These lines simulate the cursor.
The two FOR-NEXT routines are time delays. . To
speed up the flashing cursor, , shorten the loops.
To slow down the cursor, , increase the number of
loops. . The PRINT statements produce a REVERSE
FIELD, SPACE (becomes a solid block in Reverse
field), REVERSE OFF, CURSOR LEFT. This is
followed by the delay and then PRINT SPACE
and CURSOR LEFT again followed owed by a delay. By
using different characters instead of the space character
you can create some interesting cursors. This
produces an interesting wig-wag effect.
LINE 1040: The GET checks the keyboard buffer.
If it is empty (null s'ring) string) it starts the cursor
flashing again while it waits for data. Once a
character has been entered the program moves on to
the next line where it begins s to examine the nature
of the character entered.
LINE 1050-1060: These lines check for a ""delete".
LINE 1070: If ""delete" is entered and there is no
data entered the program returns to the flashing
cursor.
LINE 1080: If data has been entered this line
checks to see how long the data is. This check is
to make sure that the I' "delete" does not go past
the beginning entry point on the screen_
screen.
LINE 1090: The last character in the string is
deleted. You can continue to delete characters until
you have erased the whole string, and the program
keeps checking for the delete every time you make an
entry.
LINE 1100: You return to the flashing cursor
waiting for the next entry.
LINES 1110-1140: These lines first check to see if
you have hit "carriage return" or shifted "carriage
return". rn " . If not, then the program adds Z$ to Zl$ Z 1 $ to