High-level programming language

In the 1960s, the term autocode was commonly used to describe a high-level programming language that relied on a compiler. Notable examples of such autocodes include COBOL and Fortran. The earliest high-level programming language ever designed for computers was Plankalkül, developed by Konrad Zuse. However, it was never implemented during his lifetime, and his pioneering work remained largely disconnected from other advancements due to the disruptions of World War II. Even so, Plankalkül influenced Heinz Rutishauser’s Superplan language and, to a lesser extent, the development of ALGOL. The first high-level language to achieve widespread adoption was Fortran, a machine-independent evolution of IBM’s earlier Autocode systems. Around the same time, the ALGOL family emerged—ALGOL 58 in 1958 and ALGOL 60 in 1960—created by joint committees of European and American computer scientists. ALGOL introduced key innovations such as recursion, nested functions under lexical scope, and a clear distinction between value and name parameters with their respective semantics. It also pioneered several structured programming concepts, including the while-do loop and if-then-else statements, and became the first language whose syntax was formally defined using Backus–Naur form (BNF). Meanwhile, COBOL brought the concept of records (also known as structs) into mainstream programming, and Lisp became the first language to implement a fully general lambda abstraction. ==Abstraction penalty==

A high-level language provides features that standardize common tasks, permit rich debugging, and maintain architectural agnosticism. On the other hand, a low-level language requires the coder to work at a lower-level of abstraction which is generally more challenging, but does allow for optimizations that are not possible with a high-level language. This abstraction penalty for using a high-level language instead of a low-level language is real, but in practice, low-level optimizations rarely improve performance at the user experience level. None the less, code that needs to run quickly and efficiently may require the use of a lower-level language, even if a higher-level language would make the coding easier to write and maintain. In many cases, critical portions of a program mostly in a high-level language are coded in assembly in order to meet tight timing or memory constraints. A well-designed compiler for a high-level language can produce code comparable in efficiency to what could be coded by hand in assembly, and the higher-level abstractions sometimes allow for optimizations that beat the performance of hand-coded assembly. Since a high-level language is designed independent of a specific computing system architecture, a program written in such a language can run on any computing context with a compatible compiler or interpreter. Unlike a low-level language that is inherently tied to processor hardware, a high-level language can be improved, and new high-level languages can evolve from others with the goal of aggregating the most popular constructs with improved features. For example, Scala maintains backward compatibility with Java. Code written in Java continues to be usable even if a developer switches to Scala. This makes the transition easier and extends the lifespan of a codebase. In contrast, low-level programs rarely survive beyond the system architecture which they were written for. == Relative meaning ==

The terms high-level and low-level are inherently relative, and languages can be compared as higher or lower level to each other. Sometimes the C language is considered as either high-level or low-level depending on one's perspective. Regardless, most agree that C is higher level than assembly and lower level than most other languages. C supports constructs such as expression evaluation, parameterized and recursive functions, data types and structures which are generally not supported in assembly or directly by a processor but C does provide lower-level features such as auto-increment and pointer math. But C lacks many higher-level abstracts common in other languages such as garbage collection and a built-in string type. In the introduction of The C Programming Language (second edition) by Brian Kernighan and Dennis Ritchie, C is described as "not a very high level" language. Assembly language is higher-level than machine code, but still highly tied to the processor hardware. However, assembly may provide some higher-level features such as macros, relatively limited expressions, constants, variables, procedures, and data structures. Machine code is at a slightly higher level abstraction than the microcode or micro-operations used internally in many processors. == Execution modes ==

The source code of a high-level language may be processed in various ways, such as: ; Compiled: A compiler transforms source code into other code. In some cases, a compiler generates native machine code that is interpreted by the processor; however, many execution models today involve generating an intermediate representation (i.e. bytecode) that is later interpreted in software or converted to native code at runtime (via JIT compilation). ; Transpiled: Code may be translated into source code of another language (typically lower-level) for which a compiler or interpreter is available. JavaScript and the C are common targets for such translators. For example, C and C++ code can be seen as generated from Eiffel code when using the EiffelStudio IDE. In Eiffel, the translated process is referred to as transcompiling or transcompiled, and the Eiffel compiler as a transcompiler or source-to-source compiler. ; Software interpreted: A software interpreter performs the actions encoded in source code without generating native machine code. ; Hardware interpreted: Although uncommon, a processor with a high-level language computer architecture can process a high-level language without a compilation step. For example, the Burroughs large systems were target machines for ALGOL 60. Note that a language is not strictly interpreted or compiled. Rather, an execution model involves a compiler or an interpreter and the same language might be used with different execution models. For example, ALGOL 60 and Fortran have both been interpreted even though they were more typically compiled. Similarly, Java shows the difficulty of trying to apply these labels to languages, rather than to implementations. Java is compiled to bytecode which is then executed by either interpreting in a Java virtual machine (JVM) or JIT compiled. == See also ==