Bytes - the unit of storage
The unit of storage is the 'byte'. A single byte can hold one character from the keyboard so 10 bytes can hold 10 characters. If one byte is going to store just one character on the keyboard then we are going to need a lot of them to store a word processed document. Pictures, music, videos, games - they are all made up of instructions or data and they therefore all have a size, which is measure in bytes. A byte is actually quite small so for that reason, we frequently talk about Kilobytes, Megabytes, Gigabytes, Terabytes and so on.
1 Kilobyte (1 Kbyte) is 1024 bytes exactly, or 210 bytes exactly, or about 1000 bytes, or about a thousand bytes.
1 Megabyte (1 Mbyte) is 1048576 bytes exactly, or 220 bytes exactly, or about 1000 000 bytes, or about a million bytes.
1 Gigabyte (1 Gbyte) is 1073741824 bytes exactly, 230 bytes exactly, or about 1000 000 000 bytes, or about a thousand million bytes.
1 Terabyte (1 Tbyte) is 1099511627776 bytes exactly, 240 bytes exactly, or about 1000 000 000 000 bytes, or about a million million bytes.
So 15 Kbytes is about 15 thousand bytes. 128 Mbytes is about 128 million bytes. 20 Gbytes is about 20 thousand million bytes and so on. More often than not, you don't need to know the exact number of bytes, just an approximation!
We always measure the storage size of programs e.g. a game or an application like Word in bytes. We measure the size of any file e.g. a music file or a video file in bytes. We measure the size of different types of memory (RAM, ROM, cache) in bytes and secondary storage devices like pen drives, SD cards and hard disks in bytes. But because a byte is a very small unit, we nearly always end up talking about Megabytes or Gigabytes, for example. We should always try to put a number in the most appropriate units. For example:
32000 bytes is okay, but better is 32 Kbytes.
4000000 bytes is okay, and 4000 Kbytes is okay, but better is 4 Mbytes.
We should note, that these are approximations. 1 Mbyte is not exactly 1000000 bytes. It's actually 1048576 bytes (see above). It might be better to write the above as:
32000 bytes is okay, but better is 32 Kbytes.
4000000 bytes is okay, and 4000 Kbytes is okay, but much better is 4 Mbytes.
Q1. Write out the following numbers in approximate numbers of bytes. The first two have been done for you.
| Number | Approx number of bytes |
| a. 5 Kbytes | 5000 bytes approximately. |
| b. 6 Mbytes | 6 000 000 bytes approximately. |
| c. 20 Gbytes | |
| d. 35 Kbytes | |
| e. 55 Mbytes | |
| f. 130 KBytes | |
| g. 1000 Mbytes | |
| h. 3 Tbytes | |
| i. 6000 Kbytes |
Q2. Calculate the exact number and an approximation. The first two have been done for you.
| Number | Exact | Approx |
| a. 6 * 210 | 6144 bytes | 6 Kbyte |
| b. 15 * 212 | 61440 bytes | 61 Kbytes |
| c. 9 * 214 | ||
| d. 3 * 219 | ||
| e. 4 * 225 | ||
| f. 17 * 226 | ||
| g. 8 * 232 | ||
| h. 2 * 234 | ||
| i. 4 * 241 |
Q3. Write out these numbers of bytes in words. The first two have been done for you.
| Number | Description |
| a. 34 520 | |
| b. 751 002 | |
| c. 3 201 630 | |
| d. 34 456 789 | |
| e. 110 000 000 | |
| f. 220 000 000 | |
| g. 1 000 000 000 | |
| h. 23 000 602 022 | |
| i. 1 000 000 000 000 |
Extension work
Use the Internet to find the answers to the following:
a) What are the next four in the sequence: Kilobyte, Megabyte, GigaByte, Terabyte?
b) A byte can br broken down into a group of 8 bits. What is a group of 4 bits called?
c) Where down where the term 'bit' comes from?
d) Go to a computer store's website e.g. PCWorld. Look at some computers, laptops, ultrabooks, notebooks, tablets etc. How much memory do they come with? How much hard drive space? How much cache?
e) Look up Chromebooks. How does a Chromebook differ from a laptop? How much memory do they come with? How much hard drive space? How much cache?
f) Find out about your phone. How much internal memory does it have? Can you expand it - if so, by how much?