前几天遇到一本英文计算机书，不知该如何入类。翻来翻去，发现版权页上印有ACM Computing Classification System分类号。手头没有这个分类法，就上网去找，很容易就找到了最新的1998版，除提供浏览外，还可以将网页保存下来脱机使用。根据书上给出的类，很快就确定了《中图法》类号。
联想到在一些西文的数学书上，有时会有Mathematics Subject Classification号码。象上面的计算机图书一样，如果正好是数学小分支学科的书，这个分类法的号码很有参考价值。手头有本1980版Mathematics Subject Classification，破旧不堪，于是想到网上去看看有没有电子版的。一样很方便就找到了2000年版，除提供浏览、检索外，还可以下载PDF格式的完整版。
链接：
ACM Computing Classification System (1998 Version, valid in 2004)
美国计算机协会Association of Computing Machinery编制的计算机分类法。
2000 Mathematics Subject Classification （MSC 2000）
美国《数学评论》Mathematical Reviews和德国《数学文摘》Zentralblatt MATH所用分类法。
附二种分类一级类表：
ACM Computing Classification System一级类：
A. General Literature
B. Hardware
C. Computer Systems Organization
D. Software
E. Data
F. Theory of Computation
G. Mathematics of Computing
H. Information Systems
I. Computing Methodologies
J. Computer Applications
K. Computing Milieux
Mathematics Subject Classification一级类：
00-xx General
01-xx History and biography
03-xx Mathematical logic and foundations
04-xx This section has been deleted
05-xx Combinatorics
06-xx Order, lattices, ordered algebraic structures
08-xx General algebraic systems
11-xx Number theory
12-xx Field theory and polynomials
13-xx Commutative rings and algebras
14-xx Algebraic geometry
15-xx Linear and multilinear algebra; matrix theory
16-xx Associative rings and algebras
17-xx Nonassociative rings and algebras
18-xx Category theory; homological algebra
19-xx $K$-theory
20-xx Group theory and generalizations
22-xx Topological groups, Lie groups
26-xx Real functions
28-xx Measure and integration
30-xx Functions of a complex variable
31-xx Potential theory
32-xx Several complex variables and analytic spaces
33-xx Special functions
34-xx Ordinary differential equations
35-xx Partial differential equations
37-xx Dynamical systems and ergodic theory
39-xx Difference and functional equations
40-xx Sequences, series, summability
41-xx Approximations and expansions
42-xx Fourier analysis
43-xx Abstract harmonic analysis
44-xx Integral transforms, operational calculus
45-xx Integral equations
46-xx Functional analysis
47-xx Operator theory
49-xx Calculus of variations and optimal control; optimization
51-xx Geometry
52-xx Convex and discrete geometry
53-xx Differential geometry
54-xx General topology
55-xx Algebraic topology
57-xx Manifolds and cell complexes
58-xx Global analysis, analysis on manifolds
60-xx Probability theory and stochastic processes
62-xx Statistics
65-xx Numerical analysis
68-xx Computer science
70-xx Mechanics of particles and systems
73-xx This section has been deleted
74-xx Mechanics of deformable solids
76-xx Fluid mechanics
78-xx Optics, electromagnetic theory
80-xx Classical thermodynamics, heat transfer
81-xx Quantum theory
82-xx Statistical mechanics, structure of matter
83-xx Relativity and gravitational theory
85-xx Astronomy and astrophysics
86-xx Geophysics
90-xx Operations research, mathematical programming
91-xx Game theory, economics, social and behavioral sciences
92-xx Biology and other natural sciences
93-xx Systems theory; control
94-xx Information and communication, circuits
97-xx Mathematics education