It is important for an Auditor to have an understanding of basic computer information.

The operating speed, storage capacity, number of support devices, and system capabilities are all different measurements of a computer. An Auditor will come across all types and sizes of computers from a PC (personal computer) to a large mainframe computer system.

There are three elements involved in processing records or data. They are input, processing, and output.

INPUT. The data or source information entering the system to be processed by a computer. Input may also be computer programs that will process the data.

PROCESSING. The orderly planned actions taken by the computer (sorting, classifying, calculating, and other data operations) with the information or data that is entered into the system.

OUTPUT. The results of processed data or information. The output may be data, information, or programs. The output may be sent to a diskette, CD, tape, or printer. It may be in an easily understood format, or it may be put into a form acceptable as magnetic input for further processing.

• Addition, subtraction, multiplication, and division.
• Moving, shifting and comparing data.
• Tests conditions encountered during processing and acts accordingly.

Magnetic storage media for data may be a cartridge, tape, diskette, CD, hard disk.

Other types of storage media include microfilm, which is a photograph of documents or transactions, and microfiche, which is a photograph of documents or transactions on small (4 inches x 4 inches) plastic cards. Magnetic tape and cartridges are the principal input/output media on large mainframe computers and diskettes.

Information on magnetic tape data is:

• Stored sequentially and retained on sections.
• Recorded on parallel (channels) tracks,
• Recorded on 7, 8 or 9 tracks.
• Tape densities are usually 1600 or 6250 characters per inch.

In EBCDIC coding, columns on magnetic tape may be magnetized in nine (tracks) areas denoting or symbolizing a different character on each column. Each magnetized spot is considered a bit and a set of magnetized bits on one column is one byte.

Data is stored in bytes. One thousand (1000) bytes are called one K. For example: 64k is the same as 64000 bytes of memory.

Parity: Track number one (1) on magnetic tape is considered the parity check track. Parity may be "odd" or "even" and controls the number of magnetized spots per byte. If information is stored in "even" parity and a byte indicates an odd number of bits, then the computer is able to detect a problem in the stored information.

ASCII and EBCDIC coding formats are the most commonly used. ASCII has seven tracks plus the parity check track number one and is commonly utilized for diskettes. EBCDIC has eight tracks plus the parity check track number one and is generally used on cartridges and magnetic tapes.

The definition of binary coding indicates the presence of two possible conditions.

• On or off.
• Electrical current is present or absent.
• Data is magnetized in one direction or the other.
• Any other method in which there are only two conditions.

Symbols convey information, but the symbol itself is not the information - it only represents something that is information. Any method used to represent data is known as a code, or coding system. These codes represent alphabetic, numeric, and special characters.

The binary system uses only two symbols, 0 and 1. The symbols are called bits which is short for binary digits. The 0 represents the absence of an assigned value. The 1 represents the presence of an assigned value.

The values of the binary digits are determined by their position in a multi-digit symbol. The designer of the computer determines these values.

Types of Binary Coding

There are three basic types of binary coding that may be encountered when auditing a computerized employer.

• BCD = Binary Coded Decimal
  This coding is a six bit code and the coding can produce up to sixty-four characters.
  
  
• ASCII = American Standard Code for Information Interchange.
  This coding is a seven-bit code and the coding can produce up to one hundred twenty-eight characters.
  
  
• EBCDIC = Extended Binary Coded Decimal Interchange Code.
  This coding is an eight-bit code and the coding can produce up to two hundred fifty-six characters.

A picture clause is a description of a character and its position by a symbol representing the properties of the character.

1. Input description.
   
   A = alpha. "A" indicates the data may be only alphabetical letters or blanks.
   X = alphanumeric. "X" indicates the data may be any valid character -- numeric, alphabetic or any other character.
   9 = numeric. "9" indicates the data may be any digit or a plus/minus sign.
   S = operational symbol. "S" indicates the data in a field is signed (positive or negative). For example, S9 indicates a one digit signed numeric field.
   V = operational symbol. A "V" indicates that the numeric data has an implied decimal where indicated. For example, 99V9 indicates that the data is three digits with one decimal place.
   
   
2. Output Description
   
   Z = operational symbol. "Z" indicates the computer will suppress the display or printing of a leading zero in a field that is too large for the data.
   
   +/- = operational symbol. "+" or "-" used to display data with a positive or negative value.

A usage clause indicates the storage format of the data in each byte. The most common storage formats are display, computational, or computational-3.

1. Display: The display option specifies that the data is stored in the external decimal format. Therefore one position in storage is used for each digit in the field.
   
   
2. Computational or Comp: The option specifies that the item is stored in a binary format.
   
   
3. Computational-3 or Comp-3: The option specifies that the data is stored in an internal decimal format. When a field is converted to comp-3, all of the sign positions of the bytes are dropped except for the low-order sign that is the sign for the field. Computational fields are numeric only and are known as "packed" fields.

ILLUSTRATION OF COMP-3 (PACKED FIELD) - Conversion of numeric data from Display format to Comp-3 format. The "F" indicates the hexadecimal symbol for a signed field. The positive number 1234567 is shown below.

Display (before conversion)

F 1 F 2 F 3 F 4 F 5 F 6 F7

Comp-3 (after conversion)

1 2 3 4 5 6 7 F

The example above illustrates that one byte before conversion can hold two characters, the sign symbol and the digit. When a field is converted to comp-3, all of the sign positions of the bytes are dropped except for the low-order sign which is the sign of the field. The digits are then packed into the sign blank positions resulting in a "Packed" field. The example shows the conversion of the number 1234567 to a "Packed" field format -from requiring seven bytes storage space to four bytes of storage space. The main purpose of a "Packed" field is to save on storage space.

An operating system is a collection of programs that allows a data processing system to supervise its own operations. It acts as a gatekeeper to automatically call its programs, routines, languages, and data as needed, so that there can be a continuous uninterrupted series of jobs.

An Auditor may encounter any of these types of operating systems.

• OS Systems = large mainframe systems that primarily use magnetic tapes as storage devices.
  
  
• DOS Systems = refers to Disk Operating System. This system was developed for small and medium size computers. Diskette storage is the dominant type of auxiliary storage device for these older machines.
  
  
• Windows = currently used on many personal computers.  This type includes Windows 3.1, Window 95, Windows 98 and Windows ME (Millennium Edition), Windows XP (Home or Professional Editions), Windows Vista (Home, Professional or Ultimate Editions) and Windows 7 (Home, Professional or Ultimate Editions).
  
  
• Windows NT/Windows 2000 Professional, Windows XP Professional, Windows Vista, Windows 7= the Windows environment on a system where personal computers are networked.
  
  
• McIntosh = used on McIntosh machines. Types include Mac OS 8, Mac OS 9 and Mac OS 10.
  
  
• Unix = used on mainframe and PC systems.
  
  
• Lynx = (pronounced Lennix) used on PC's.

JCL is a language used to write job-control statements that tell large computer systems what kind of jobs and job steps are to be run. The statements link the data and devices together for processing.

JCL is used to:

• Print reports on the system printer.
• Access data stored on the mainframe.
• Access software on the mainframe, such as SAS, Syncsort, etc.
• Access utility programs on the mainframe.

The different statements in the JCL are:

1. JOB statement. This marks the beginning of a job and is often referred to as a JOB Card. The statement identifies:

2. EXEC Statement. This marks the beginning of a job step. It instructs the computer to execute a particular program. The statement identifies:

3. DD Statement. This defines the data to be used in a job step. The statement identifies the datasets to be read or the datasets that will receive the output. The statements may include parameters to:

4. Other job control statements.