May June 1980 - Commodore Computers

'VlA MAY/JUNE. Y I 1980 198O ISSUE 4 A COMPUTE. 69
In lhil thh ISSllr, issue, J/llrlerle Marlmt I'mllo Pmtiu amlillllll continues /itr her/JrtUlIlalioTl presentation of the .I:radi".1!. gradingprogram
lshown llUll-'1l i1l m hIssue SIl,. 3's 3 C/Jlumll. column, 711 '/'his time tape (Illd anddisl.. dish data Jtomge storage 0/)/1011$ upturns are
added. Re RCLL
The Learning Lab
Marlene Protto
Pratfo
This grading program originated on a 32 K PET
This grading program originated on a 32K PET
withoUl without a printer. Its major idea was to mail1lain
maintain
the information in thee machine in arrays for easy
reviewing and recording of thee results by hand. Op·
lions tions are now provided for storingg and retrieving eving the
partial or full term data on tape or disk (tape refers to
partial or full term data on tape or disk (tape refers to
cassette tape 110 I/O and disk refers to the CBM 2040 disk
drive 110 , whil e 110 refers to input/output opera­
drive I/O. while I/O refers to input/output opera
ti0l1S).
tions).
The user is asked how the data will be entered
The user is asked how the data will be entered
(statements 2905-2907) and there is a new item in thee
menu (s tatements 27620-27640) allowing th e data to be
menu (statements 27620-27640) allowing the data to be
saved. Of the numeric data, only thee raw student
grades are stored. When thee data is read from tape or
disk thee user r may choose to add grades if the total
number of grades will not exceed thee maximum in
2150. The averages, z scores, and frequencies encies are then
recalculated and the menu presented.
.
As thee average are calculated, thee user is asked
is the average is "okay". If a change is needed and
the inpUl input came from tape orr disk, all off the current
scores are printed to refresh the user's memory
(statements 13200-13560). 3560). If the user wants to review
the grades, he/she may ask to change one grade and
merelyy input the same mc value. Note that a change of
input method was made here in order to speed up
the program (13250). If you prefer using the return
key, do not make this s change.
The instructions concerning g grade changes have
been modified. For r each student the user may Illay
change all grades or one grade at a time (13600-
change all grades or one grade at a time ( 13600-
14000).
14000).
Since the scores may come from more than one
input source, two twO variables are needed to keep track
of the number of grades from frolll each. A new variable
NN is used for the number of grades entered
NN is used for th e number of grades entered
initially and NP is th e number of grades added on a
initially and NP is the number of grades added on a
subsequent run. . In the first case N =NN= N
and in
the second case N = N N + N P.
the second case N ~ I N + NP.
Writing the Data File
Observe statements 36010-36097. RV Rv is a variable
which points to where the program should continue cO lllinue
if there is an I/O 110 problem and IT refers to disk
or o r tape. The filename and an indicator for r tape or o r
the disk drive number are requested.
The form of the OPEN statement is OPEN
parml, parmi, parm2, parm3, parm4 pann4 where parml I is the
logical file number, parm 2 is the device number
(DV), (Dv), parm3 is the secondary address (SA), and parm4
is the c filename and/or commands. cO lllmands. The variables, DV
and SA, are arc assigned differently for tape or disk
(36024 & 36028). The disk filename is modified as
shown in 36028. 36028, The fourth parameter consists of the
drive nUllIber number (either 0 ur or I) 1) lo followed by a
: (colon),
the e name provided by the e user and finally indicators
for SEQuential file type aand WRITE mode of operation.
In additiun addition, . forr disk 110. I/O, we OPEN OPKN the com· comerrorr
channel in order to check for disk eerrors.
rs .
We choose to use file number 2 and we must use
Secondary Address 15. Some form of initialization
of the disk drive muSt must occur. It is included in the
OPEN command by using g ""I" I " + HS H$ as the fourth
parameter where H$ is the disk drive number provided
by the user. (We are assuming that the diskette
has been formatted at this pain!.)
point.)
Tape fil filee writing is indicated by a Secondary
Address of I. 1. Disk filee writing is indicated by filee
type (SEQ) and mode (WRITE) which arc are part of the
fourth parameter in the OPEN statement. In either
case, the first parameter is the filee number which
will later appear after the # in the PRINT#
statements. nt s .
IT is checked in 36032. If thee userr has not
responded with Tor T 0 orr 1, thee program relUrn returnss
to 36022 to elicit the proper resonse.
Information is written to the external medium in
the following ow g order: I) 1) filee identifier (32 characters
or less off information), n), 2) number of students, , 3)
number of grades per student, and 4) a character
(0$) (DS) to indicate whether identifiers have been provided
by the user or if sequence numbers will be written
as identifiers.
For r each cach student slUdclll an identifier or sequence ence number
and the e student's grades are written. After the last(Jth)
stUth)
student's data, , DONE E is written. The user is informed
when the file e writing is completed complcted and is returned relUrned
to the menu.
Reading the Data File
e
The 'rhe program asks s how data is to be read
(2905-2907). If the data comes from tape or disk, the
filename is entered ered (2925), and the e DeVice number
and a Secondary Address are arc set (2930-2935).
Tape file reading is indicated by a Secondary
Address of O. For di sk, the founh parameter is
Address of 0. For disk, the fourth parameter is
similar to that for writing, except that the mode is
replaced by READ. The error channel is opened and
the disk drive is initialized (this s may occur twice in
the program since the e read and write portions are
independent of each other and a the user may choose
any y of several combinations of I/O 110 options.) File
1I is opened for either disk d or tape reading. Student
data are arc read in 10250 and 11560.
Data as Character Strings
The data are written as character strings. On input
the data are read as character strings and converted
to numeric data as needed. Microsoft BASIC provides
two functions for converting convening data from numeric
to character characler and character to numeric. . STR$(numeric
variable) will convert a number to a string, slrin while
VAL(string V variable) will convert a string to a number.