1.6. Characters

In English or most of western languages, the number of alphanumeric characters is less than \(256\). Hence, all characters can be encoded in one byte (\(8\)-bit) binary string. In US, the encoding map is known as American Standard Code for Information Interchange or ASCII. The lower and upper cases of all letters and various symbols are encoded in 8-bit strings. For example, ‘A’=1000001B and ‘a’=1100001B. (B at the end indicates that it is a binary string.) Note that integer 1=00000001B and character ‘1’=00110001B in ASCII are two different things. Sending 00000001B to a printer does not print 1. You need to convert a number to a character string. When you type ‘1’ on a keyboard, you are sending character ‘1’ to computer. You need to convert it to integer. I/O functions do that automatically. You can convert manually from a number to a character string using funtion str(). To concert a character string to a corresponding integr, use functionint(). See Example below.

Some languages use a lot more characters than \(256\). For example, Chinese language uses several thousand characters. Therefore, \(8\)-bit string is not large enough. Two-byte (\(16\)-bit) strings can encode \(65536\) characters, which seems large enough for all languages.

In python, character strings are enclosed in “…” or ‘…’, for example ‘Hello world!’.

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Example 1.2.1: Converstion from a character string to the corresponding integer.

Let us convert character string ‘365’ to integer \(365\) using int().

int('365')

365

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Example 1.2.2: Converstion from an integer to the corresponding character string.

Try to convert integer \(365\) to character string ‘365’ using str().

str(365)

'365'

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Example 1.2.3:

“print” function automatically converts numbers to characters and send it to display.

x=365
a=print(x)

365

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Example 1.2.4: Conversion using variables.

We store an integer 365 in a variable x, then convert it to character and store it in another variable c. Using an enquirer function type(), we can check the type of the variables. Notice that printout of x and c are identical but their type is different.

x = 365
print("x=",x," and  its type is ",type(x))
c = str(x)
print("c=",c," and  its type is ",type(c))

x= 365  and  its type is  <class 'int'>
c= 365  and  its type is  <class 'str'>

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Last modified on 02/09/2024 by R. Kawai.