In digital electronics and computer hardware, which of the following circuits is specifically designed to store exactly one bit of data, holding a value of either 0 or 1 until it is changed by a control signal?

Introduction / Context:
This question is about basic building blocks of digital electronics used in computer hardware. Digital systems are based on binary information, and to implement memory and state, circuits must be able to hold a value of 0 or 1 until some event causes a change. The fundamental storage unit at the circuit level is known as a flip flop. Understanding that a flip flop stores one bit of data helps connect low level hardware concepts to higher level notions such as registers and memory cells.

Given Data / Assumptions:

• The question asks which circuit is used to store one bit of data.
• The options include register, flip flop, vector, and encoder.
• We assume a standard digital logic context where circuits are built from logic gates and used to store and process binary information.
• We also assume that one bit refers to a single binary value that can be either 0 or 1.

Concept / Approach:
A flip flop is a bistable circuit, meaning it has two stable states. It can store a single bit by remaining in one of these states until a control input, such as a clock or set or reset signal, causes it to change. Different types of flip flops, such as SR, JK, D, or T flip flops, are used depending on design needs, but all serve the core function of storing one bit. A register is a group of flip flops arranged together to store multiple bits, such as 8 or 16 bits. A vector is a concept from mathematics and programming that represents an ordered list of values, not a physical circuit. An encoder converts one type of binary code into another but is not used solely for storage.

Step-by-Step Solution:
Step 1: Focus on the requirement to store exactly one bit of data, which implies a circuit with two stable states.Step 2: Recall that a flip flop is defined as a bistable circuit that can hold either a 0 or a 1 until its input causes a state change.Step 3: Note that a register consists of multiple flip flops and therefore stores multiple bits rather than a single bit alone.Step 4: Recognize that vector and encoder are not storage circuits but represent abstraction or code conversion functions.Step 5: Conclude that the flip flop is the circuit specifically designed to store one bit of data.

Verification / Alternative check:
Digital design textbooks show memory cells built from flip flops or latch circuits. Diagrams of registers label each box as a flip flop holding one bit, and then groups of these boxes are combined to store multi bit values. Hardware description languages such as VHDL or Verilog also describe registers as arrays of flip flops. No standard reference describes a single register element as storing just one bit without mentioning flip flops. This consistent treatment confirms that the correct answer for a circuit that stores one bit is flip flop.

Why Other Options Are Wrong:
Option A is incorrect because a register is a collection of flip flops used for storing several bits in parallel, not the smallest unit that holds one bit. Option C is incorrect because a vector is a mathematical and programming concept and does not refer to a physical digital circuit. Option D is incorrect because an encoder changes code representations but does not primarily store a bit over time. Only option B, flip flop, a bistable circuit that can store a single bit of data, accurately fits the description given in the question.

Common Pitfalls:
Students sometimes confuse registers and flip flops because both terms appear when discussing CPU registers and memory. Another pitfall is assuming that any component that handles bits can be called memory, even if it only processes them briefly. It is useful to remember the hierarchy: flip flops implement one bit of storage, registers combine multiple flip flops, and larger memories combine many registers and arrays of cells. Keeping this hierarchy in mind clarifies how simple circuits scale up to form complex storage subsystems in modern computers.

Final Answer:
The correct answer is Flip Flop, a bistable circuit that can store a single bit of data.