TECHNICIAN’S GUIDE TO PROGRAMMABLE CONTROLLERS (BORDEN/COX) 7TH ED.
| CHAPTERS 1–13 COMPLETE EXAM REVIEW | 100% VERIFIED Q&A | PASS
GUARANTEE
1. What is a programmable controller (PLC)?
ANSWER : A PLC is a solid-state, industrial-grade digital computer
designed to perform control functions using programmable memory to
store instructions and execute functions such as logic, sequencing,
timing, counting, and arithmetic.
2. Who is credited with developing the first programmable
controller, and in what year?
ANSWER : Dick Morley of Bedford Associates is credited with
developing the first PLC in 1968 for General Motors to replace relay-
based control systems.
3. What were the main disadvantages of relay control panels that
PLCs were designed to overcome?
ANSWER : Relay panels were bulky, difficult to modify, consumed
significant power, had mechanical contacts that wore out, were hard to
troubleshoot, and required extensive rewiring for any program change.
4. List the five basic sections of a PLC system.
ANSWER : The five basic sections are: (1) the power supply, (2) the
central processing unit (CPU), (3) the input/output (I/O) section, (4) the
memory section, and (5) the programming device.
5. What is the function of the CPU in a PLC?
ANSWER : The CPU executes the user program stored in memory,
processes input signals, makes control decisions based on programmed
logic, and updates output signals accordingly.
,6. Define 'scan' as it applies to PLC operation.
ANSWER : A scan is one complete cycle of PLC operation consisting
of: reading all inputs, executing the user program, updating all outputs,
and performing housekeeping/communication tasks.
7. What is scan time, and why is it important?
ANSWER : Scan time is the time required to complete one full scan
cycle. It is important because it determines how quickly the PLC can
respond to changes in input conditions; faster scan times mean faster
system response.
8. What does the acronym PLC stand for?
ANSWER : PLC stands for Programmable Logic Controller.
9. What is the difference between a fixed (brick) PLC and a modular
PLC?
ANSWER : A fixed (brick) PLC has a set number of I/O points built into
one housing and cannot be expanded, while a modular PLC uses a
chassis or rack with separate plug-in modules allowing the system to be
expanded and customized.
10. Name three industries that commonly use PLCs.
ANSWER : PLCs are commonly used in automotive manufacturing,
food and beverage processing, and water/wastewater treatment plants.
CHAPTER 2 — NUMBER SYSTEMS AND CODES (Q11–20)
11. Convert the binary number 1011 to its decimal equivalent.
ANSWER : 1×2³ + 0×2² + 1×2¹ + 1×2⁰ = 8 + 0 + 2 + 1 = 11 (decimal).
12. Convert the decimal number 25 to binary.
ANSWER : 25 ÷ 2 = 12 R1, 12 ÷ 2 = 6 R0, 6 ÷ 2 = 3 R0, 3 ÷ 2 = 1 R1, 1
÷ 2 = 0 R1. Reading remainders upward: 11001₂.
13. What is the hexadecimal equivalent of the binary number
11110000?
ANSWER : Group into nibbles: 1111 = F, 0000 = 0. The hexadecimal
equivalent is F0₁₆.
, 14. What does BCD stand for, and how is the decimal number 93
represented in BCD?
ANSWER : BCD stands for Binary Coded Decimal. The number 93 in
BCD is: 9 = 1001, 3 = 0011, so BCD = 1001 0011.
15. What is the octal equivalent of decimal 64?
ANSWER : 64 ÷ 8 = 8 R0, 8 ÷ 8 = 1 R0, 1 ÷ 8 = 0 R1. Reading
remainders upward: 100₈.
16. How many bits are in one byte?
ANSWER : One byte contains 8 bits.
17. What is the largest decimal value that can be represented by an
8-bit binary number?
ANSWER : The largest value is 2⁸ − 1 = 255.
18. What is the Gray code, and why is it used in industrial
applications?
ANSWER : Gray code is a binary numbering system where adjacent
values differ by only one bit. It is used in shaft encoders and position
sensors to prevent errors during transitions between states.
19. What is two's complement representation used for in PLCs?
ANSWER : Two's complement is used to represent negative numbers in
binary, allowing the CPU to perform subtraction using addition circuits.
20. Convert hexadecimal 3A to decimal.
ANSWER : 3×16¹ + A×16⁰ = 3×16 + 10×1 = 48 + 10 = 58 (decimal).
CHAPTER 3 — PLC HARDWARE COMPONENTS (Q21–30)
21. What is the purpose of the power supply in a PLC system?
ANSWER : The power supply converts AC line voltage to the regulated
DC voltages (typically 5 VDC and 24 VDC) required by the CPU,
memory, and I/O circuits.
22. What types of memory are found in a PLC?
| CHAPTERS 1–13 COMPLETE EXAM REVIEW | 100% VERIFIED Q&A | PASS
GUARANTEE
1. What is a programmable controller (PLC)?
ANSWER : A PLC is a solid-state, industrial-grade digital computer
designed to perform control functions using programmable memory to
store instructions and execute functions such as logic, sequencing,
timing, counting, and arithmetic.
2. Who is credited with developing the first programmable
controller, and in what year?
ANSWER : Dick Morley of Bedford Associates is credited with
developing the first PLC in 1968 for General Motors to replace relay-
based control systems.
3. What were the main disadvantages of relay control panels that
PLCs were designed to overcome?
ANSWER : Relay panels were bulky, difficult to modify, consumed
significant power, had mechanical contacts that wore out, were hard to
troubleshoot, and required extensive rewiring for any program change.
4. List the five basic sections of a PLC system.
ANSWER : The five basic sections are: (1) the power supply, (2) the
central processing unit (CPU), (3) the input/output (I/O) section, (4) the
memory section, and (5) the programming device.
5. What is the function of the CPU in a PLC?
ANSWER : The CPU executes the user program stored in memory,
processes input signals, makes control decisions based on programmed
logic, and updates output signals accordingly.
,6. Define 'scan' as it applies to PLC operation.
ANSWER : A scan is one complete cycle of PLC operation consisting
of: reading all inputs, executing the user program, updating all outputs,
and performing housekeeping/communication tasks.
7. What is scan time, and why is it important?
ANSWER : Scan time is the time required to complete one full scan
cycle. It is important because it determines how quickly the PLC can
respond to changes in input conditions; faster scan times mean faster
system response.
8. What does the acronym PLC stand for?
ANSWER : PLC stands for Programmable Logic Controller.
9. What is the difference between a fixed (brick) PLC and a modular
PLC?
ANSWER : A fixed (brick) PLC has a set number of I/O points built into
one housing and cannot be expanded, while a modular PLC uses a
chassis or rack with separate plug-in modules allowing the system to be
expanded and customized.
10. Name three industries that commonly use PLCs.
ANSWER : PLCs are commonly used in automotive manufacturing,
food and beverage processing, and water/wastewater treatment plants.
CHAPTER 2 — NUMBER SYSTEMS AND CODES (Q11–20)
11. Convert the binary number 1011 to its decimal equivalent.
ANSWER : 1×2³ + 0×2² + 1×2¹ + 1×2⁰ = 8 + 0 + 2 + 1 = 11 (decimal).
12. Convert the decimal number 25 to binary.
ANSWER : 25 ÷ 2 = 12 R1, 12 ÷ 2 = 6 R0, 6 ÷ 2 = 3 R0, 3 ÷ 2 = 1 R1, 1
÷ 2 = 0 R1. Reading remainders upward: 11001₂.
13. What is the hexadecimal equivalent of the binary number
11110000?
ANSWER : Group into nibbles: 1111 = F, 0000 = 0. The hexadecimal
equivalent is F0₁₆.
, 14. What does BCD stand for, and how is the decimal number 93
represented in BCD?
ANSWER : BCD stands for Binary Coded Decimal. The number 93 in
BCD is: 9 = 1001, 3 = 0011, so BCD = 1001 0011.
15. What is the octal equivalent of decimal 64?
ANSWER : 64 ÷ 8 = 8 R0, 8 ÷ 8 = 1 R0, 1 ÷ 8 = 0 R1. Reading
remainders upward: 100₈.
16. How many bits are in one byte?
ANSWER : One byte contains 8 bits.
17. What is the largest decimal value that can be represented by an
8-bit binary number?
ANSWER : The largest value is 2⁸ − 1 = 255.
18. What is the Gray code, and why is it used in industrial
applications?
ANSWER : Gray code is a binary numbering system where adjacent
values differ by only one bit. It is used in shaft encoders and position
sensors to prevent errors during transitions between states.
19. What is two's complement representation used for in PLCs?
ANSWER : Two's complement is used to represent negative numbers in
binary, allowing the CPU to perform subtraction using addition circuits.
20. Convert hexadecimal 3A to decimal.
ANSWER : 3×16¹ + A×16⁰ = 3×16 + 10×1 = 48 + 10 = 58 (decimal).
CHAPTER 3 — PLC HARDWARE COMPONENTS (Q21–30)
21. What is the purpose of the power supply in a PLC system?
ANSWER : The power supply converts AC line voltage to the regulated
DC voltages (typically 5 VDC and 24 VDC) required by the CPU,
memory, and I/O circuits.
22. What types of memory are found in a PLC?
