← ACARA Digital Technologies Years 7–8

Why digital hardware has two states

A tiny electronic switch that is either off (0) or on (1), so it holds exactly one bit. Digital hardware joins millions of them to work with data.

Part of: ACARA Digital Technologies Years 7–8 — Representing Text, Images and Sound — Module 4, ACARA Digital Technologies Years 7–8 — Binary Number Representation — Module 26

Understanding Why digital hardware has two states in ACARA Digital Technologies Years 7–8

What it does: Current flowing means on, and on is written as the bit 1. Every transistor holds exactly one bit, so millions of transistors working together can hold millions of bits. A transistor works like a very small switch. It is either off or on, and that gives two states. A switch has only two states. Off is written as 0 and on is written as 1. One switch has two states, so it holds one bit. Eight bits would need eight switches. In digital hardware the bit 0 stands for the off state, where no current flows. The broken code reverses the rule, but off (no current) is 0 and on (current) is 1.

Common mistakes: A single = assigns a value. To check whether the transistor is on, the condition needs the comparison operator ==. An if line must end with a colon. It should be: if current:.

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This module's key terms are also in a printable crossword (Modules 69–124) and word search (Modules 69–152).

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Learning
Duo
What is a transistor in digital hardware?
A tiny screen that shows picturesA tiny electronic switch that is off or on
Matches
A transistor has ten states, 0 to 9
↓
A transistor has only two states, off and on. Ten states is how denary works, not how digital hardware switches work.
Applying
Meanings
Term
transistor
Meaning
A tiny electronic switch that is either off (0) or on (1), so it holds exactly one bit. Digital hardware joins millions of them to work with data.
Practice
IF transistor = OFF THEN
Testing
Gaps
IF current = THEN state ← "off"
Check Answer
Spots
2bit = 0
3if transistor = "on":

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Quick Questions

1. What is a transistor in digital hardware?
A. A tiny electronic switch that is off or on ✓
B. A tiny screen that shows pictures
A transistor works like a very small switch. It is either off or on, and that gives two states.
2. Which pair shows the two states of one switch?
A. Low (2) and high (5)
B. Off (0) and on (1) ✓
A switch has only two states. Off is written as 0 and on is written as 1.
3. A switch has no electric current flowing. Which bit does it hold?
A. 0 ✓
B. 1
No current means off, and off is the bit 0. Current flowing means on, which is the bit 1.
4. How many bits can ONE transistor switch hold?
A. Exactly one bit ✓
B. Eight bits
One switch has two states, so it holds one bit. Eight bits would need eight switches.
5. How does digital hardware handle large amounts of data?
A. One giant switch stores everything
B. Millions of switches work together ✓
Each switch holds only one bit. Hardware joins millions of them, so together they can work with lots of data.

Match the Pairs

transistor → A tiny electronic switch inside a chip that is either off or on, so it holds exactly one bit
0 → No current flowing through a switch (off)
A switch that has current flowing is in the on state, which stores the bit 1 → current = on = 1
A chip joins millions of two-state switches, so each one holds one bit → 1 transistor = 1 bit
A transistor has ten states, 0 to 9 → A transistor has only two states, off and on. Ten states is how denary works, not how digital hardware switches work.
no current = 1, current = 0 → The values are swapped. No current is 0 and current is 1.

Key Term

transistor
A tiny electronic switch that is either off (0) or on (1), so it holds exactly one bit. Digital hardware joins millions of them to work with data.

Fill in the Blanks

1. IF current = 0 THEN state ← "off"
Hint: Type the digit that stands for no current flowing
2. IF current = 1 THEN state ← "on"
Hint: Type the digit that stands for current flowing
3. bitsPerTransistor ← 1
Hint: Type how many bits one transistor switch can hold
4. totalBits ← switchCount * bitsPerSwitch
Hint: Type the operator that multiplies, to find the total bits from many switches
5. FOR EACH transistor IN chip bitCount ← bitCount + 1
Hint: Type the keyword that goes between the loop variable and the collection it loops over

Spot the Error

Question 1
A transistor = "off"
B bit = 0
C if transistor = "on":
D bit = 1
E print(bit)
Line C — A single = assigns a value. To check whether the transistor is on, the condition needs the comparison operator ==.
Question 2
A current = False
B if current
C bit = 1
D else:
E bit = 0
Line B — An if line must end with a colon. It should be: if current:
Question 3
A switches = 4
B states = 2 * switches
C print(states)
Line B — Each switch has 2 states, so the number of combinations is 2 to the power of the switches. It should be 2 ** switches, which gives 16, not 8.
Question 4
A current = True
B bit = 0
C if current:
D bit = 2
E print(bit)
Line D — A transistor is either off or on, so it can only hold the bit 0 or 1. When current flows, the bit should be 1.
Question 5
A switches = [0, 1, 1, 0]
B on = 0
C for s in switches:
D on = on + switch
E print(on, "switches are on")
Line D — The loop variable is called s, so switch does not exist and causes an error. It should be on = on + s.

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