Recs.
Updated
SpecsUpdate
Pros
Pro Extremely efficient
The C language's mentality is to trust the programmer. With all great powers comes great responsibilities. C allows you to harness the full power of the underlying hardware.
No garbage collection is a blessing, not a curse. It forces the programmer to be aware of what he's writing. It's similar to getting frustrated with spoken languages because they don't have built-in autocorrect. Although it's easier to brainlessly write a text and let autocorrect do the work for you, you won't become better in the language this way, nor will you be able to better express yourself because you don't have to think about the grammar of the language.
Having to think about resources and how to best implement everything, coupled with the relatively low-level of C in general. Makes C programs extremely efficient and fast.
Pro Portable
C is portable between most hardware. Generally a C compiler is made for any new architecture, and already exists for existing architectures.
C is portable between all operating systems (Windows, UNIX and Mac) and only needs a program to be recompiled to work. This allows anyone on any operating system to learn about the language and not be held back by intricacies of their operating system.
With this said, C's portability these days is not quite what it used to be. Much of said portability relies on the POSIX standard in particular, and as time passes, the compliance of a given system with that standard is becoming less certain; especially in the case of Linux. Most things will still be portable (or at least emulatable) between Windows, Linux, and FreeBSD for example; but you will at times need to make use of platform-specific support libraries for certain individual cases, as well.
Pro Understanding of computers
Learning C forces you to grapple with the low-level workings of your computer (memory management, pointers, etc.) in ways that the other languages abstract away. Without an understanding of these low-level aspects of computer programming you will be limited if you try to develop an application that needs to run in a memory or performance constrained environment.
Other languages like Python can obscure a lot of details, so your foundation may be weaker.
Pro Very compact
C is compact and very fast. It is ideal for embedded programming, which requires only small resources. C is straight forward and very portable especially in a Unix environment.
Most popular languages are descendant from C. C programmers do not requires any fancies like class, template or overloading, etc. Those not only make for confusion, but also bloat the object code. Efficient C code utilizes every bit of the machine it is running on.
Pro Low level of abstraction
While higher level languages languages like Java and Python provide possibilities to be "more expressive" per line of code, it's much more convenient to start with "less efficient" (get me right) language, in order to get initial concepts of how things behave at lower level.
Actually C is a good starting point moving to both higher and lower levels of abstraction, the good example here would be learning C before Assembler, as for general use the Assembler quite hard to understand due to low level of its abstraction (like getting the understanding on how loops work in C before trying to implement them on Assembler).
Pro Pleasing to the programmer
Whether you are writing application code or trying to code-golf something down to the fewest bytes and milliseconds (perhaps both at the same time) possible, as opposed to languages such as C++, notoriously painful to read and debug, C's simplicity at its heart will make the job much less annoying.
Pro Portable between CPU architectures
C was designed to be independent of any particular machine architecture, and so with a little care, it is easy to write "portable" programs (see here). By design, C provides constructs that map efficiently to typical machine instructions, and therefore it has found lasting use in applications that had formerly been coded in assembly language like operating systems or small embedded systems.
Pro Foundational, difficult but important
Learning C will teach valuable skills and transferrable understanding of computing. While learning a scripting language may be easier, students will not understand system constraints and performance problems, nor what features like garbage collection are actually doing in other languages.
Cons
Con Unsafe
C makes it extremely easy to make mistakes. Your language should help you be productive by abstracting mistakes away from you.
Con Lack of support for first class strings
C does not support the string type, nor does it support UTF-8 strings that modern languages are employing today. Instead of strings, C makes use of the *char type which is a pointer to a character array.
Con Language is full of corner cases and undefined behaviors
Undefined behavior in a program can cause unexpected results, making it hard to debug. With UB, program behavior may vary wildly depending on optimization settings. There are many cases that invoke UB, such as signed overflow, invalid dereferences, large integer shifts, uninitialized variables, etc. These serve to frustrate novice programmers when they could be learning other concepts.
Con Arrays are not first class objects
When an array is passed to a function, it is converted to a pointer, even though the prototype confusingly says it's an array. When this conversion happens, all array type information gets lost. C arrays also cannot not be resized, which means that even simple aggregates like a stack are complicated to implement. C arrays also cannot be bounds checked, because they don't know what the array bounds are.
Con Does not support modules; header file annoyances
Header files are a poor man's implementation of modules. Modern programming languages make use of modules which eliminate the need for C includes and header files and the many issues caused by them, such as the complete lack of dependency checking.
Header files often contain even more include statements that point to other header files which also point to even more which drastically increases compile time. Modules only have to be compiled once, and when importing those modules into your software project, you only have to pull in the module that you are using, which is often times already precompiled.
This way, the compiler knows exactly what it needs before beginning to compile your project and can automatically compile the few dependencies it needs in advance rather than recursively compiling every header file it runs across as in C.
Con Completely lacks type safety
The C standard library is not type safe, and the language itself does not promote type safety built into the language, which leads to error-proneness of the language. If anything, it would be recommended that those interested in C to instead put their time in D, which actually includes a complete copy of the C standard library rewritten to be fully type safe.
Con Only offers basic support for source code split into multiple files
Modern programming languages are capable of compiling split source code files by concatenating them together efficiently at compile time before compiling them. However, C requires the developer to resort to messing with header files and makefiles to get similar functionality.
Con Includes require obscene resources to compile
All the modern languages have resulted in ditching the ancient deprecated model of #include statements and have instead adopted the superior model of modules. When compiling software written in C, the programmer is forced to also compile X headers which contain Y headers which contain Z headers and so forth -- drastically increasing the number of lines that need to be compiled. In order to compile something as simple as "Hello, World", for example, 18K lines of code needs to be compiled. This can be very taxing on RAM and CPU resources, causing compile times to quickly absorb a large portion of the programming process.
Recommendations
Comments
Flagged Pros + Cons
Pro If you can't grok C you should not be a professional programmer
It sets an early bar that if you can't hurdle you might as well do something other than programming and not waste any more of your time.