Basic Pascal Tutorial/Chapter 1/Assignment and Operations: what changed

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Title: Basic Pascal Tutorial/Chapter 1/Assignment and Operations

New		Line
1	+	1E - Assignment and Operations (author: Tao Yue, state: unchanged)
2	+
3	+	Once you have declared a variable, you can store values in it. This is called assignment.
4	+
5	+	To assign a value to a variable, follow this syntax:
6	+
7	+	``` pascal
8	+	variable_name := expression;
9	+	```
10	+
11	+	Note that unlike other languages, whose assignment operator is just an equals sign, Pascal uses a colon followed by an equals sign, similarly to how it's done in most computer algebra systems.
12	+
13	+	The expression can either be a single value:
14	+
15	+	``` pascal
16	+	some_real := 385.385837;
17	+	```
18	+
19	+	or it can be an arithmetic sequence:
20	+
21	+	``` pascal
22	+	some_real := 37573.5 * 37593 + 385.8 / 367.1;
23	+	```
24	+
25	+	The arithmetic operators in Pascal are:
26	+
27	+	\| Operator \| Operation \| Operands \| Result \|
28	+	\|----------\|-------------------------------\|-----------------\|-----------------\|
29	+	\| \+ \| Addition or unary positive \| real or integer \| real or integer \|
30	+	\| \- \| Subtraction or unary negative \| real or integer \| real or integer \|
31	+	\| * \| Multiplication \| real or integer \| real or integer \|
32	+	\| / \| Real division \| real or integer \| real \|
33	+	\| div \| Integer division \| integer \| integer \|
34	+	\| mod \| Modulus (remainder division) \| integer \| integer \|
35	+
36	+	`div` and `mod` only work on integers. `/` works on both reals and integers but will always yield a real answer. The other operations work on both reals and integers. When mixing integers and reals, the result will always be a real since data loss would result otherwise. This is why Pascal uses two different operations for division and integer division. `7 / 2 = 3.5` (real), but `7 div 2 = 3` (and `7 mod 2 = 1` since that's the remainder).
37	+
38	+	Each variable can only be assigned a value that is of the same data type. Thus, you cannot assign a real value to an integer variable. However, certain data types will convert to a higher data type. This is most often done when assigning integer values to real variables. Suppose you had this variable declaration section:
39	+
40	+	``` pascal
41	+	var
42	+	some_int : integer;
43	+	some_real : real;
44	+	```
45	+
46	+	When the following block of statements executes:
47	+
48	+	``` pascal
49	+	some_int := 375;
50	+	some_real := some_int;
51	+	```
52	+
53	+	`some_real` will have a value of `375.0`.
54	+
55	+	Changing one data type to another is referred to as typecasting. Modern Pascal compilers support explicit typecasting in the manner of C, with a slightly different syntax. However, typecasting is usually used in low-level situations and in connection with object-oriented programming, and a beginning programming student will not need to use it. Here is [information on typecasting from the GNU Pascal manual](http://www.gnu-pascal.de/gpc-es/Type-Casts.html).
56	+
57	+	In Pascal, the minus sign can be used to make a value negative. The plus sign can also be used to make a value positive, but is typically left out since values default to positive.
58	+
59	+	Do not attempt to use two operators side by side, like in:
60	+
61	+	``` pascal
62	+	some_real := 37.5 * -2;
63	+	```
64	+
65	+	This may make perfect sense to you, since you're trying to multiply by negative-2. However, Pascal will be confused — it won't know whether to multiply or subtract. You can avoid this by using parentheses to clarify:
66	+
67	+	``` pascal
68	+	some_real := 37.5 * (-2);
69	+	```
70	+
71	+	The computer follows an order of operations similar to the one that you follow when you do arithmetic. Multiplication and division (`* / div mod`) come before addition and subtraction (`+ -`), and parentheses always take precedence. So, for example, the value of: `3.5*(2+3)` will be `17.5.`
72	+
73	+	Pascal cannot perform standard arithmetic operations on Booleans. There is a special set of Boolean operations. Also, you should not perform arithmetic operations on characters.
74	+
75	+	---
76	+	From the Free Pascal wiki, page "Basic Pascal Tutorial/Chapter 1/Assignment and Operations", as it stood on 2022-08-20 after a change by Kai Burghardt, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).

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