Transcript CHAPTER 1

Chapter 1
Introduction to CBIS
Information Technology
Trends
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“free” hardware
easy-to-use software
pre-packaged software
small computers
data availability
data variety
mass storage
technologies
• convergence of
technologies
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networks
internet
mass marketing
reduction of barriers
non-accounting use of IT
new sys development
approaches
• intelligent systems
• business re-engineering
Competitive Advantage
– sales
• data warehousing/data mining
– service
• workflow, imaging, etc.
– production
• cad/cam
– management
• ais, dss/es, eis, ems
Roles for Accountants
• Challenges
– IT changing organization structure,
management, operations
– IT changing nature and economics of
accounting
– IT changing competitive environment
• Opportunities
– user role
– information design, development
– management and control of IT
– system evaluation/audit
Information System Control
and Audit
• multi-disciplinary field
– audit
– IT management
– behavioural science
– computer science
Key Dimensions of Practice
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process integrity
auditability
compliance
security
availability
development practices
value for money
Introduction to CBIS concepts
• people
• infrastructure
• software
• files/data
• procedures/controls
• transaction processing
– transaction
processing phases
– access methods
– transaction
processing modes
– devices
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input
transmission
output
storage
Files
• Data structures - list, array, table, file, database
• File components - file label, header & trailer records
• Header - file name, id creation date
• Trailer - # of records, end of file
• Records, Fields, Bytes and Bits
• Record - made up of fields
• Field - made up of chars (each of A 123 etc.) - byte
• Each char - coded comb. of information units - bits
Files (cont’d)
•Fixed /variable length records
•fixed - size and number of fields are defined in
advance, easiest to work with
•variable - size defined but not number, except for
maximum
•Master Files and Transaction Files (use sales example)
•master file - semi -permanent info. - customer #, name,
address, credit limit, and a/r balance
•transaction file - customer #, invoice #, date, amount
and other invoice data
•table
Transaction Processing Phases
•Transaction initiation - data capture
•Input preparation - coding of data
•Transmission/input - via LAN etc.
•Processing
•Output
•Error correction and reprocessing
Access Methods
•Sequential - ascending/descending - customer # - must
be kept in order- slow in searches as must always search
from beginning - updates are also slower as must read
and recreate entire master file - normally on tape
•Direct/random - each record accessed independently,
very fast - normally stored on magnetic disk, each record
assigned a specific physical address..harder to program
for as must create storage address conversion algorithm
•Indexed sequential access - combines benefits of each 2 parts- data records & index that contains record keys
and storage addresses. Data can be accessed either
sequentially or directly
Access Methods -2
•Data base - data management is completely separate
from programs (unlike other 3 above)
•no duplication of data or redundancy
•data is stored only once
•data base management system allows various programs
to access data for processing
Transaction Processing Modes
•On-line - direct interaction
•Batch vs transaction
•Batch
•all trans are grouped via a logical basis and processed at one point
(e.g. inventory then sales then a/r) very economical but slow
•Transaction
•source data processed by transaction
•Centralized vs decentralized (distributed) systems
•distributed used more as networks/communications
faster
INPUT DEVICES
•Punched cards - old old old
•Keyboards, mice
•Key to tape/Key to disk
•for data accumulation
•several work stations to central disk
•MICR (magnetic ink character recog’n- cheques)
•OCR (optical character recog’n)
COMMUNICATION DEVICES
•Networks - 2 or more computers linked by comm lines
•LANs (one building) and WANs (several buildings)
•STAR, RING, and BUS topologies
•Modems
•Routers
•Transmission lines
OUTPUT MEDIA and STORAGE DEVICES
•Printers
•Microfilm/microfiche
•Digital image processing
•Diskettes
•Hard disks
•Tapes
•use parity checking to check against tape errorsextra bit used to check the first eight
•CD-ROMS and WORMS
CPU
•Control Section - directs and coordinates all EDP system
operations
•Arithmetic/Logic unit - does math calcs + what if logic
•Main memory - storage for Control section and ALU
•Stored Program concept - all programs stored within
computer’s memory for execution.
•Registers - designed for temp storage and are capable of
receiving, holding and transferring info. (e.g. address
register, operation code register, etc.)
•Instructions - group of bits that tells computer to perform
basic functions
Control
• availability: backup, recovery, disaster plans
• security: privacy/confidentiality
• integrity: completeness, accuracy, authorization
• maintainability/evolvability
• auditability: management trails
• value for money