Week 15 · Term 1 review (Chapters 1–13) and your own mini-project · 3 lessons
2
Review: numbers, computers, networks, data and models
ICT Secondary 1 Term 1, Review: pp. 4–202
GoalReview the ideas of Weeks 4 to 12 with new calculations: numbers, sizes, logic, networks, tables and statistics.
New words
bit / byte · 0 or 1 / 8 bitsselection / projection · choose rows / choose columnsmean / median / mode · average / middle value / most common valuehalf adder · adds two bits: sum = XOR, carry = AND
Explanation
Number systems. 45 in binary: 45 = 32 + 8 + 4 + 1, so 101101. Grouped in fours that is 0010 1101, so 2D in hexadecimal. Back the other way, hex 3F is 3 × 16 + 15 = 63, and binary 1101 0110 is D6. Sizes. For sound and images we use decimal units here (1 KB = 1,000 B). Sound at 8,000 samples per second, 16 bits per sample, 10 seconds, one channel: 8,000 × 16 × 10 = 1,280,000 bits, divided by 8 gives 160,000 bytes = 160 KB. An image 200 × 100 pixels at 8 bits per pixel: 20,000 × 8 ÷ 8 = 20,000 B = 20 KB. Logic. A half adder with inputs 1 and 1 gives sum = 1 XOR 1 = 0 and carry = 1 AND 1 = 1, which is binary 10. Networks. An IPv4 number has four parts from 0 to 255, so 192.168.1.300 is not valid. Tables. In the Books table, selecting Copies > 2 keeps whole rows (Sky Atlas and Number Games); projecting Title keeps the whole column. Statistics. For 4, 8, 6, 10, 6: the mean is 34 ÷ 5 = 6.8, the median (sorted 4, 6, 6, 8, 10) is 6, and the mode is 6.
Task
Working
Answer
45 to binary
32 + 8 + 4 + 1
101101
hex 3F to decimal
3 × 16 + 15
63
sound size
8,000 × 16 × 10 ÷ 8
160,000 B
image size
200 × 100 × 8 ÷ 8
20,000 B
Worked examples
ID
Title
Copies
B1
Sky Atlas
3
B2
Desert Stories
1
B3
Number Games
4
B4
Garden Notes
2
The Books table of an invented club. Selection by Copies > 2 gives two rows; projection of Title gives one column.
A
B
Sum
Carry
0
0
0
0
0
1
1
0
1
0
1
0
1
1
0
1
The half adder for all four input pairs. The sum is XOR and the carry is AND.
Measure
Working
Value
mean
(4 + 8 + 6 + 10 + 6) ÷ 5
6.8
median
4, 6, 6, 8, 10
6
mode
6 appears twice
6
Mean, median and mode of 4, 8, 6, 10, 6 in a table.
Class activity
On paper, make your own five tasks, one each from numbers, sizes, logic, tables and statistics, with working and answers. Use this convention: 1 KB = 1,000 B for sound and image, and say it in the task.
Practice
1
Write 13 in binary.
1101 (8 + 4 + 1).
2
An image 100 × 50 pixels at 8 bits per pixel. What is its size in KB (1 KB = 1,000 B)?
