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+[\<- Notes 01/31](01-31.md)
+
+---
+
+# Arrays of Linked Lists
+
+- Linked Lists can be initialized as follow:
+
+```
+#define NODE struct node
+
+struct node{
+	char name[20];
+	int size;
+	NODE *next;
+};
+
+struct list{
+	NODE *head;
+	NODE *tail;
+};
+
+struct list x[4];
+```
+
+- Now you have 4 linked lists in `x`, each with a head and tail
+- Inserting and deleting should be the same, just specify which element in the `x` array you are inserting/deleting
+
+---
+
+# Files
+
+- Two kinds of files we will cover:
+
+## Text Files
+
+- Colletions of characters saved in a secondary storage
+- No fixed size
+- End file with `<eof>`
+- End of lines are marked with `('\n')`
+
+Example:
+
+```
+This is a text file!<newline>
+It has two lines.<newline><eof>
+```
+
+The actual file will look like this:
+
+```
+This is a text file!<newline>It has two lines.<newline><eof>
+```
+
+- All textual **input** and **output** data are actually a continuous **stream** of character codes
+	- We refer to a data source or destinations as an **input stream** or an **output stream**
+	- These general terms can be applied to:
+		- files
+		- the keyboard
+		- the screen
+		- any other source of input data or destinations of output data
+
+- Keyboard and Screen
+	- **stdin**
+		- keyboard's input stream
+	- **stdout**
+		- "normal" output stream associated with the screen
+	- **stderr**
+		- "error" output stream associated with the screen
+	- **Streams are treated like text files**
+		- Their individual components are characters
+
+- **To read from stdin**
+
+```
+r = scanf("%d", &num);
+```
+or
+```
+ch = getchar();
+```
+
+- **The characters are read sequentially**
+	- Consecutive calls to scanf and/or getchar will read **consecutive elements** from the keyboard
+	- ^D usually represents `<eof>`
+
+- **scanf**
+	- Returns how many elements were read
+	- Placeholders define the type
+	
+	- Examples:
+
+```
+%c, %d, %f, %s
+```
+
+	- **For limiting the size of a string**
+		- %Ns - reads up to N characters (array size should be N+1)
+	- **For lines**
+
+```
+r = scanf("%[^'\n']", string_name);
+```
+
+	- Only reads the characters as specified by the placeholder
+		- Spacers (\n, \t, or spaces) may be left in the buffer from previous calls
+	- **To clear buffer:**
+		- fpurge() - erases any input or output buffered in the given stream
+		- Example:
+
+```
+fpurge(stdin);
+r = scanf("%[^'\n']", string_name);
+```
+
+- **To read lines**
+	- fgets(array, SIZE, stdin);
+		- Includes the \n at the end of the line
+		- If used after scanf, may need to clear the buffer
+
+- **To write to stdout**
+	- `printf("%d", num);` or `putchar(ch);`
+
+- **The file is written sequentially**
+	- Consecutive calls to `printf` and/or `putchar` will write **consecutive elements** to the file
+
+## Working with Text Files
+
+```
+FILE *infp
+
+if((infp = fopen("data.txt", "r")) == NULL) printf("cannot open the file dat.txt\n"); //failsafe
+```
+
+- The file is always open for reading from the beginning
+
+- To open a text file for reading when the **name is stored in a string:**
+
+```
+char file_name[50];
+FILE *infp;
+
+if((infp = fopen(file_name, "r")) == NULL) printf("cannot open");
+```
+
+- **To read from the text file**
+
+```
+ret = fscanf(infp, "%d", &num);
+```
+or
+```
+ch = getc(infp);
+```
+
+- The file is read **sequentially**
+- **Returned value**
+	- fscanf -- number of values converted 
+	- getc -- the character read (returns EOF at end of file)
+
+- Open a text file for writing from the **beginning**:
+
+```
+char file_name[50];
+FILE *outfp;
+
+if((outfp = fopen(file_name, "w")) == NULL) printf("Cannot open the file %s\n", file_name);
+```
+
+- Open a text file for writing from the **end**:
+	
+```
+char file_name[50];
+FILE *outfp;
+
+if((outfp = fopen(file_name, "a")) == NULL) printf("cannot open the file %s\n", file_name);
+```
+
+- To **Write** to a text file:
+
+```
+fprintf(outfp, "%d", num);
+```
+or
+```
+putc(ch, outfp);
+```
+
+- The file is written sequentially
+	- Consecutive calls to fprintf and/or putc will write consecutive elements to the file
+
+- To **Close** a text file:
+
+```
+fclose(infp);
+fclose(outfp);
+```
+
+---
+
+[-> Notes 02/10](02-10.md)