of blank tape is written by giving either the MWA
or MWB order. An end of file is written as follows: 1) Four MWA commands
write three inches of blank tape. 2) Then end of file character is
written by giving the MPS order.

Information is read and checked for correct parity while writing.

If too many program steps are given between the motion select command,
MWA or MWB and the first MPS, the unit will deselect (or disconnect).
The MPS is then a no-operation command.

_Writing Program_

As an example, a program to write k words in binary format from storage
beginning in register A, using tape unit number 04, is shown. The
following program is written in standard FRAP language. The program
begins in register enterwrite.

enterwrite mec ,clear flags initially
mwb 400 ,73000000464
lir x/-k+1 ,initialize index register x
b lio x/a+k-1 ,begin loop
mps ,wait for TC then write C(Z)
jmp c ,error
spx x/1 ,add 1 to index register x
jmp b ,return of loop
jmp done ,record written

c mec ,tape error
ril 1
spi
jmp rwcstop ,read-write error or tape fault
ril 1
spi
jmp b+3 ,tape end
hlt ,tape parity

done ,resume programming

_Reading Information_

Information is read by giving the MRA or MRB order. Almost 10 ms. is
available after a read order is given before information actually enters
the TC buffer.

To read a record of unknown length, the read order is first given. The
MPS order halts the program until six characters are assembled in the TC
information buffer. The next instruction after the MPS, a jump
instruction, transfers control from the loop when any flag is set. The
next instruction deposits the IO. The record length is determined by not
skipping after the MPS order on the setting of the end of record flag.
The read-write check flag or the end of record flag is then interrogated
to see that the tape is actually at the end of record. If a tape is not
at the end of record, then the tape is either at the end of the reel, or
a parity check has occurred.

_Reading Program_

Program to read j binary words into storage be