The Stored Program; Exercises - IBM 7090 Instruction-Reference

The program for this problem is made up of instructions and data channel commands
that control the 7090 to perform the operations outlined. These instructions and com-
mands progress step-by-step and the control section recognizes each in turn when the
previous operation is complete.
Because the control section of the system operates at electronic speed and the card
reader and printer are relatively slow, it is apparent that much communication is nec-
essary between the mechanical functions and the control section. The control section
must wait until A and B have been read from the card before adding them together. The
sum C can be developed and stored at electronic speed, but must wait in storage until
the printer is ready to receive it for printing.
Figure
1.
4-1 shows the progression of the steps in the foregoing program. Not
shown in Figure 1.4-1 are the instructions and commands that initiate each of the oper-
ations depicted. These are also in storage along with the factors A and B and constitute
the stored program. As each instruction ends its operation, the next instruction is
called out and initiates its operation. In this manner, the 7090 system progresses
through the solution according to the program in storage.
1. 4.01 The Stored Program
The program previously described used CPU instructions and data channel commands
from storage. These instructions controlled other information going to and from stor-
age. But how did the instructions and commands get into storage? In the beginning,
the author of the program decides what instructions and commands to use and in what
order to use them. There are several ways to get these instructions and commands in-
to storage without a stored program already in the system. Among these ways are
direct manual entry from the operator's keys on the IBM 7151 Console Control Unit
*,
entry from cards or tape caused by a command manually entered into a data channel
from the IBM 7617 Data Channel Console
*,
and forced automatic operation of a card
reader or tape unit caused by depression of a load key on the CPU console.
\Vh.atever the means of entry, both the stored program instructions and the data to
be processed must be previously translated into machine language in the form of binary
words. A binary word, as used in the 7090, consists of 36 binary positions. The bin-
ary number system is explained in Appendix A of IBM 7090 Data Processing System
Reference Manual, Form A22-6528. Also explained there are processes for conversion
of decimal numbers to binary numbers, and binary numbers to decimal numbers. A
third system (called octal) provides a quicker and less cumbersome means of expressing
binary numbers.
1.
4. 02 Exercises
The following equivalent numbers in binary, octal, and decimal provide an opportun-
ity to practice conversion from one number system to another. Do the conversions and
check your results against those given. (Decimal and octal fractions are rounded to
three places and binary fractions are rounded to nine places.)
*
The CPU console (IBM 7151) is a separate machine type, and there is only one on each 7090 system.
Each 7607 Data Channel has a manual console of its own (IBM 7617).
10