Skip to main content

CR, LF, and CRLF

One of the confusing aspects for people working across multiple platforms is the newline character. Mac OS, Windows, and Linux all use different characters for newline. Even Mac OS behaves differently between older and newer versions. In this article, we will explore the reasons behind the different newline characters used across systems.

According to the ISO 6429 standard, LF (line feed, \n) moves the cursor to the next line while maintaining the current column, and CR (carriage return, \r) moves the cursor to the beginning of the current line. To achieve the newline function, both CR and LF should be used together. This distinction was made to mimic the behavior of early printers and typewriters that separated the line-changing action from the action of moving the cursor to the beginning.


For instance, a string "A\nB" should not result in B directly below A, but rather B should appear diagonally below A, like in the above example. However, systems using CRLF as a newline character are rare. Storage is a relatively cheap resource nowadays, but in the past, it was quite expensive. System designers of that time considered allocating two bytes for newline characters to be an excessive expense. Consequently, some system designers began using either LF or CR as the sole newline character.

Amidst this, some systems adhered to the standard. One such operating system was CP/M, which used a combination of CR and LF for newline characters. This choice was not simply due to the desire to follow the standard but was a strategic decision to maintain compatibility with earlier remote terminal devices. In other words, the costly storage expense was deemed worthwhile to secure market dominance by maintaining backward compatibility. Some subsequent operating systems also made the same choice, one of which was Microsoft's MS-DOS. This choice continues today, with Microsoft Windows using CRLF as its newline character.

Among the operating systems that chose to reduce newline characters to a single byte, there were different preferences. Some designers chose LF as the newline character, while others picked CR. Multics, an operating system that later influenced the design of Unix and BSD, chose LF. Though Multics is no longer in use, Unix-like systems, including Linux, adopted LF and move the cursor to the beginning of the next line when encountering LF.

Apple was a prominent supporter of using CR as the newline character. The Apple II, created in 1977, used CR for newline and simply ignored LF. This choice was carried over to Mac OS. However, with the creation of the POSIX.1 (Portable Operating System Interface) standard in 1988, Unix-based operating systems, including Linux, began to prioritize compatibility with one another. As a result, Apple started to change as well. Eventually, in 2001, OS X adopted LF as its newline character, making systems using CR as the newline character increasingly rare. Currently, aside from some legacy Apple programs, only LF and CRLF exist.


Popular posts from this blog

[C++] Handling Exceptions in Constructors

When you use RAII idiom, there are often situations where constructors have to do complex tasks. These complex tasks can sometimes fail, resulting in throwing exceptions. This raises a concern: Is it okay to throw exceptions in constructors? The first concern is memory leaks. Fortunately, memory leaks do not occur. Variables created on the stack are released through stack unwinding, and if an exception occurs during heap allocation with the new operator, the new operator automatically deallocates the memory and returns nullptr . The next concern is whether the destructor of the member variables will be called correctly. However, this is also not a problem. When an exception occurs, member variables can be divided into three categories: fully initialized member variables, member variables being initialized, and uninitialized member variables. Fully initialized member variables have had their constructors called and memory allocations completed successfully. In the example code, t

Iterator Adapters in Rust

An Iterator that takes another iterator and returns a new one is called an iterator adapter . The name "adapter" comes from one of the GoF's design patterns, the adapter pattern . However, in reality, it corresponds more to the decorator pattern , so if you pay too much attention to the name, you might get confused about its purpose. So it's better not to worry too much about the name. Enough complaining about the name, what does an iterator adapter do? An iterator adapter adds a task to be performed when the iterator iterates. This will be easier to understand when you see an example. The map function is one of the famous adapters. The iterator returned by the map function for those who have used functional languages iterates over new values transformed from the original values. Besides, various adapters are already implemented in the standard library. Among them, the most frequently used are those that are convenient to use with loops. Examples include the

What is the size of an empty object?

Consider a class like the one above. Commonly called an "empty class," this class has no internal variables. So, how big is this empty class? At first glance, the size should be 0 since there are no member variables. However, the size is never 0 in any language, whether Java, C#, C (in this case, a struct), or C++. This is to ensure that two different objects never have the same address. Empty classes typically have a size of 1 byte in a 32-bit environment and 2 bytes in a 64-bit environment. However, the exact size cannot be determined. According to the specification, the size just needs to be non-zero. The precise size depends on the implementation. This is a translation of my old Korean post written in 2015. Because the size can vary depending on the implementation, it is now possible to have different sizes (although still not 0). And Languages like Rust have even introduced zero-sized types . We will look at this topic in more detail at a future opportunity.