课题：
请在下列英文例题中列出特定词语的个数。
条件：
将以下句子作为txt文件保存后,在程序中读取文件使用。
输入存在于下文的"单词"时输出如下。
1960s - 2
英文内容：Terminology invoking "objects" and "oriented" in the modern sense of object-oriented programming made its first appearance at MIT in the late 1950s and early 1960s.
In the environment of the artificial intelligence group, as early as 1960, "object" could refer to identified items (LISP atoms) with properties (attributes) Alan Kay was later to cite a detailed understanding of LISP internals as a strong influence on his thinking in 1966.
Another early MIT example was Sketchpad created by Ivan Sutherland in 1960-61 in the glossary of the 1963 technical report based on his dissertation about Sketchpad, Sutherland defined notions of "object" and "instance" (with the class concept covered by "master" or "definition"), albeit specialized to graphical interaction.
Also, an MIT ALGOL version, AED-0, established a direct link between data structures ("plexes", in that dialect) and procedures, prefiguring what were later termed "messages", "methods", and "member functions".
In the 1960s, object-oriented programming was put into practice with the Simula language, which introduced important concepts that are today an essential part of object-oriented programming, such as class and object, inheritance, and dynamic binding.
Simula was also designed to take account of programming and data security.
For programming security purposes a detection process was implemented so that through reference counts a last resort garbage collector deleted unused objects in the random-access memory (RAM).
But although the idea of data objects had already been established by 1965, data encapsulation through levels of scope for variables, such as private (-) and public (+), were not implemented in Simula because it would have required the accessing procedures to be also hidden.
