Programs & Defining Data

Ch.5 – pp. 95-109

Data in Computer Memory

G E 3EGRO 289934

480

481

482

483

484

485

490

See page 69

480

481

482

Byte locations in memory -One character per byte location

483

Data in Memory

G = C7 = 1100 0111E = C5 = 1100 0101O = D6 = 1101 0110R = D9 = 1101 1001G = C7 = 1100 0111E = C5 = 1100 01013 = F3 = 1111 00114 = F4 = 1111 0100

480

The characters shown in memory are really made up of binary digits (bits) as depicted to the right. In a mainframe computer, the bits are configured as EBCDIC whereas in a PC, the bit configurations are different, in ASCII. Are you comfortable with ASCII and EBCDIC? Are you comfortable with binary/hexadecimal data configurations? If not, check out your textbook on pages: 68-76 in Ch.4

Decimal Binary Hex

0 0000 0

1 0001 1

2 0010 2

3 0011 3

4 0100 4

5 0101 5

6 0110 6

7 0111 7

8 1000 8

9 1001 9

10 1010 A

11 1011 B

12 1100 C

13 1101 D

14 1110 E

15 1111 F

16 1 0000 10

Hexadecimal conversion chart – the same as shown in your text on page 70.

Representing Data

1 Character = 1 Byte = 2 Hex Digits

Representing Character Data

Left justified - padded with blanks (40)- truncated to the right

Example:

GEORGE = C7 C5 D6 D9 C7 C5

Define Storage / Constant

[label] DS CLnn

[label] DC CLnn’character data’

Defining Storage

• Reserve Storage with no initialization• See Data Definitions topic beginning p.103• Used to allow a symbolic name for an area of memory• symbolicname DS definition

1-8 alphanumeric characters1st must be alphabetic

1. Duplication factor2. Type code3. Length

Defining Storage Example

• Output buffer area that will be printed – allows each sub-field to be identified and accessed symbolically and the entire area can also be accessed as OWKAREA. Example:

• MOVE OWKPRICE,INVCOST *MOVE COST TO PRICEMOVE OWKONHND,INVHAND *MOVE ONHAND TO ONHANDPUT OUTFILE,OWKAREA *PRINT ENTIRE O/P RECORD

OWKAREA DS 0CL50 OWKITNBR DS CL5 OWKITDES DS CL20 DS CL5 OWKPRICE DS CL5 OWKORDPT DS CL5 OWKONHND DS CL5 OWKONORD DS CL5

p. 103

5 20 5 5555

OWKAREA

OWKITNBROWKITDES

OWKPRICEOWKORDPT

OWKONHNDOWKONORD

The numbers within the orange boxes represent the field lengths in bytes. The labels represent the subfield name (statement label). The entire field (made up of 7 subfields) constitutes the output buffer. Each subfield can be manipulated, then accessed together and in the same order as parts of OWKAREA

And the Memory Reserved?

UNPK OWKPRICE(5),PPRICE Print from OWKAREA

[label] DS CLnn

[label] DC CLnn

TEN DC CL2’10’ HRLY_PAY DC CL5’17.65’ DATE DC CL6’020807’ (MMDDYY) MONTH DC C’FEBRUARY’ LENGTH IMPLIED = 8 BYTES DEPTNO DC CL3’CIS’

Another Example?

Initializing Storage Areas

Define Constants – DC, rather than DS

ABC DC C’ABC’ C1 C2 C3

DSIGN DC C’$’ 5B

NO3 DC C’3’ F3

NAME DC C’JOE’ D1 D6 C5

TAXRT DC C’28’ F2 F8

[label] DS CLnn

[label] DC CLnn

EMPL-IN DS 0CL80 EMPLOYEE INPUT BUFFER EMPL-NO DS CL6 EMPL. SERIAL NUMBER DS CL1 EMPL-NM DS CL20 EMPL. NAME (LAST, FIRST, MI) DS CL1 EMPL-HRS DS CL4 HOURS WORKED (NN.N) DS CL1 EMPL-CD DS CL2 PAY CODE TO DETERMINE PAY RT DS CL1 EMPL-DT DS CL6 DATE (MMDDYY) DS CL38

Example (w/instructions)

CALC PACK RATE(4),TAXRT

PACK TAXAMT(6),TOTINC

MP TAXAMT(6),RATE

UNPK INCTAX(8),TAXAMT(6)

…..

RATE DS F

TAXRT DC CL2’20’ *F2 F0

TAXAMT DS PL6

TOTINC DC CL’40000’ *F4 F0 F0 F0 F0

INCTAX DS CL8

Other Data Types

[label] DS/DC C character

X hex

P packed dec.

B binary

F fullword (bin)

H halfword (bin)

D doubleword

Representing Zoned Decimal

Numbers are left justified, also padded to the right with blanks(same as character data)

1234 = F1 F2 F3 F4 F1 F2 F3 C4

DATE DC CL8'020807'

Feb. 8, 2007

Representing Packed Decimal

Right justified, padded with leading zeroes

+1234 = 0001234C

-1234 = 0001234D

PAYRATE DC PL5'1785'

The top value is positive and the sign character is the right-most part of the value in memory. The lower value is negative. Notice the difference in the sign character.

Representing Binary Data

• 1 byte = 8 binary digits (bits)• 1011 0110 (B6)• Halfword = 2 bytes• Fullword = 4 bytes

BIN22 DC BL2'00010110'

BIN22 DC F’22'

The top value, defined as binary digits with length of 2 bytes in memory appears just as the value appears in the DC operand (but with 8 bits of leading 0’s as padding). On the other hand, when defined as a fullword (also binary), in memory, the 1-bits are no different, but there would be 4 bytes instead of 2 bytes –

‘0000 0000 0000 0000 0000 0000 0001 0110’

Convert Binary to Decimal

0 0 1 1 0 0 1 0 1 0 0 1

2048 1024 512 256 128 64 32 16 8 4 2 1

1 + 8 + 32 + 256 + 512 = 809

Assign positional values to each binary digit beginning on the right – right-most bit is 2º, next bit to the left is 21, then 22, and so forth. Then simply add up the equivalent decimal values where there are 1-bits in the binary field above.

Use the Scientific Calculator

Calculators are found under the Accessories menu when you ‘click’ on the START button in the lower left corner of your screen.For the Scientific Calculator, click on the VIEW menu in the Calculator Window and choose ‘Scientific’ …Enter your DEC number, then ‘Click’ the BIN button to convert Dec Bin

Convert Decimal to Binary

• Use the table on the top of page 75 that shows converting hex to decimal, but use it in reverse.

• Example: convert 1517810 to hex• Using entire table, find smallest number less than the

number you are attempting to convert which is 12,228 which is hex 3000 (in Byte 3 in left-hand column). Record the Hex value on your piece of paper…3000.

• Subtract 12,228 from the original number – which is 2890• Find next smallest number again in the next column to

the right (2816). Record the Hex value … B00• And so on until you are at the far right column (64 and

10). Record the Hex values … 40 and A• 3B4A in hex is 0011 1011 0100 1010 in binary answer.• Or use the Scientific Calculator

See the process on the next slide

Hex Dec Hex Dec Hex Dec Hex Dec Hex Dec

0 0 0 0 0 0 0 0 0 0

1 65,536 1 4,096 1 256 1 16 1 1

2 131,072 2 8,192 2 512 2 32 2 2

3 196,608 3 12,228 3 768 3 48 3 3

4 262,144 4 16,384 4 1,024 4 64 4 4

5 327,880 5 20,480 5 1,280 5 80 5 5

6 393,216 6 24,576 6 1,536 6 96 6 6

7 458,752 7 28,672 7 1,792 7 112 7 7

8 524,288 8 32,768 8 2,048 8 128 8 8

9 589,824 9 36,864 9 2,304 9 144 9 9

A 655,360 A 40,960 A 2,560 A 160 A 10

B 720,896 B 45,056 B 2,816 B 176 B 11

C 786,432 C 49,152 C 3,072 C 192 C 12

D 851,968 D 53,248 D 3,328 D 208 D 13

E 917,504 E 57,344 E 3,584 E 224 E 14

F 983,040 F 61,440 F 3,840 F 240 F 15

4

10 = A

A

15,178 =

15178- 12288

2890

1

3

2 2890- 2816

74

B

3 74 - 64

10

4

Or - Convert Doing the Arithmetic

15178 / 16 = 948.625Remainder .625 is integer .625 X 16 = 10 (A)

948 / 16 = 59.25Remainder .25 is integer .25 X 16 = 4 (4)

59 / 16 = 3.6875Remainder .6875 is integer .6875 X 16 = 11 (B)

3/16 = 0.1875Remainder .1875 is integer .1875 X 16 = 3 (3)

Using result in reverse order = 3B4A

Converting Zoned to Packed Decimal

• Use the PACK instruction (p.84 & 85)

• Read a number from an input file. It is now in memory in zoned-decimal format – you cannot do arithmetic on it, so PACK it first (PACK removes the zones)

• PACK removes all the zones except the right-most, then reverses the right-most byte

See examples on the next slide

Book Examples

Receiving Sending

Before: 99 99 99 F1 F2 F3 F4 F5

After: 12 34 5F F1 F2 F3 F4 F5

Before: 00 00 00 00 F2 F6 F4 F8

After: 00 02 64 8F F2 F6 F4 F8

Before: 00 00 F6 F3 F2 F0 F4

After: 20 4F F6 F3 F2 F0 F4

p. 84/85

PACK RECEIVING,SENDING

Converting Packed to Zoned Decimal

• Use the UNPK instruction (p. 85)• You have completed performing arithmetic on a value and you

wish to print it – packed decimal data is not printable• UNPK puts zones back in the numbers and reverses the two

right-most characters.

See examples on the next slide

Book Examples

Receiving Sending

Before: 00 00 00 00 00 56 43 7F

After: F5 F6 F4 F3 F7 56 43 7F

Before: 00 00 00 00 00 03 4C

After: F0 F0 F0 F3 C4 03 4C

Before: 00 00 13 91 2D

After: F1 D2 13 91 2D

p. 85

UNPK RECEIVING,SENDING

Quick Review of Data

ZD = F2 F0 F5 F5 F9 F7 F4 F7 F4PD = 20 55 97 47 4FHex = 0C 41 2B 22Bin = 0000 1100 0100 0001

0010 1011 0010 0010

p. 76

Instruction Formats

Page 76 - bottom

Instruction Lengths

op code R1 R2

op code M1 M2

2 addresses – sending and receiving fields

op code R1 M2M2

Sending and Receiving Fields(A Reminder)

Receiving Sending

Before: F0 F4 F3 F9 F9 F0 F0 F7 F0 F1

After: F0 F0 F7 F0 F1 F0 F0 F7 F0 F1

See page 77 at the top

A Typical 6-byte Instruction

Address 2Length Address 1Op. Code

0 8 16 32

Instruction Format:

D2 0-255 D1 D2B1 B2

Example: Move Characters

MVC D1(L,B1),D2(B2)

MVC OUTAREA(10),INAREA

Sample 4-byte Instruction

Op. Code R1 D2

0 8 12 31

X2(Index)

16

Instruction Format:

5C R1 X2 D2

Example:

M INC,TAXTABLE(RIX)

M R1,D2(X2,B2)

B2

B2

And A 2-byte Instruction

Op. Code R1 R2

Instruction Format:

0 8 12 15

Example:

1A R1 R2

AR REG2,REG1

AR R1,R2

Decimal Arithmetic

• Add Decimal • AP M1(L1),M2(L2) 6-byte

format

M1(L1) M2(L2)

Before: 10 00 0F 01 0F

After: 10 01 0C 01 0F

Before: 87 11 0F 40 00 0F

After: 27 11 0C 40 00 0F

In the 2nd Add: high-order digit overflowed and lost

Decimal Arithmetic

• Subtract Decimal• SP M1(L1),M2(L2) 6-byte format

M1(L1) M2(L2)

Before: 10 00 0F 75 0F

After: 09 25 0C 75 0F

Decimal Arithmetic

• Multiply Decimal• MP M1(L1),M2(L2)

– L1 has a max length of 16 bytes– L2 has a max length of 8 bytes

M1(L1) M2(L2)

Before: 00 00 8C 50 0F

After: 04 00 0C 50 0F

Decimal Arithmetic

• Divide Decimal• DP M1(L1),M2(L2) 6-byte format

M1(L1) M2(L2)

Before: 00 00 00 05 3C 00 7C

After: 00 00 7C 00 4C 00 7C

Quotient Remainder – length of divisor

Before the instruction is executed, M2 is the divisor, M1 is the dividend. L1 and L2 are the lengths of each

Decimal Arithmetic

• Zero-And-Add Packed• ZAP M1(L1),M2(L2) 6-byte format• More like a Move instruction than an Add Instruction

M1(L1) M2(L2)

Before: 12 45 9C 1C

After: 00 00 1C 1C